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While @Floris has answered it in almost totality, I wanted to add one more significant aspect of the wings.

On earth, when we try to generate movement in a body (or even to keep the body stable), in general, there are two forces we need to tackle with (ignoring friction etc.) - the inertia of the body and the weight of the body.
It is possible to find ways to outsource fighting-the-gravity part (i.e. balancing weight fully or partially) to something, so that we can direct our forces in overcoming the inertia as much as possible. Wings represent such an arrangement.

If we bring an aircraft to zero-speed mid-air and stop the engines, it will not have the same downward acceleration as it would have had if it didn't have wings.

So, wings fight gravity on their own (even if they don't get any help from the engine) - to some extent, by using their shape against some properties of the surrounding fluid (air). This is something that engine can't do.

So, a good part of the work done by engine can now be spared from fighting gravity. This is how a thrust-to-weight ratio of less than $1$ can lift the aircraft.

If air was liquid, absolutely no work would be needed by the engine for fighting gravity, and all its thrust could be used for forward movement.
On the other hand, if air had no fluid properties (like pressure etc.), all the fight against gravity would be required to come from engine (thrust $\ge$ weight). An aircraft in air is somewhere in between.

This is somewhat like inclined plane where the plane takes some fighting with gravity (i.e. balances part of the weight), and hence less force than the weight of the body is needed for causing a vertical component of displacement of the body.

While @Floris has answered it in almost totality, I wanted to add one more significant aspect of the wings.

On earth, when we try to generate movement in a body (or even to keep the body stable), in general, there are two forces we need to tackle with (ignoring friction etc.) - the inertia of the body and the weight of the body.
It is possible to find ways to outsource fighting-the-gravity part (i.e. balancing weight fully or partially) to something, so that we can direct our forces in overcoming the inertia as much as possible. Wings represent such an arrangement.

If we bring an aircraft to zero-speed mid-air and stop the engines, it will not have the same downward acceleration as it would have had if it didn't have wings.

So, wings fight gravity on their own (even if they don't get any help from the engine), by using their shape and angle of attack against some properties of the surrounding fluid (air). This is something that engine can't do.

So, a good part of the work done by engine can now be spared from fighting gravity. This is how a thrust-to-weight ratio of less than $1$ can lift the aircraft.

If air was liquid, absolutely no work would be needed by the engine for fighting gravity, and all its thrust could be used for forward movement.
On the other hand, if air had no fluid properties (like pressure etc.), all the fight against gravity would be required to come from engine (thrust $\ge$ weight). An aircraft in air is somewhere in between.

This is somewhat like inclined plane where the plane takes some fighting with gravity (i.e. balances part of the weight), and hence, additionally, less force than the weight of the body is needed for supporting the weight of the body.

While @Floris has answered it in almost totality, I wanted to add one more significant aspect of the wings.

On earth, when we try to generate movement in a body (or even to keep the body stable), in general, there are two forces we need to tackle with (ignoring friction etc.) - the inertia of the body and the weight of the body.
The trick is to find ways to outsource fighting-the-gravity part (i.e. balancing weight fully or partially) to something, so that we can direct our forces in overcoming the inertia as much as possible. Wings represent such an arrangement.

A clump of iron would sink in water whereas a saucer of the same weight will not. Similarly, if we bring an aircraft to zero-speed mid-air and stop the engines, it will not have the same downward acceleration as it would have had if it didn't have wings.

So, wings fight gravity on their own (even if they don't get any help from the engine) - to some extent, by using their shape against some properties of the surrounding fluid (air). This is something that engine can't do.

So, a good part of the work done by engine can now be spared from fighting gravity. This is how a thrust-to-weight ratio of less than $1$ can lift the aircraft.

If air was liquid, absolutely no work would be needed by the engine for fighting gravity, and all its thrust could be used for forward movement.
On the other hand, if air had no fluid properties (like pressure etc.), all the fight against gravity would be required to come from engine (thrust $\ge$ weight). An aircraft in air is somewhere in between.

This is somewhat like inclined plane where the rigidity of the body takes some fighting with gravity (i.e. balances part of the weight), and hence less force than the weight of the body is needed for causing a vertical component of displacement of the body.

While @Floris has answered it in almost totality, I wanted to add one more significant aspect of the wings.

On earth, when we try to generate movement in a body (or even to keep the body stable), in general, there are two forces we need to tackle with (ignoring friction etc.) - the inertia of the body and the weight of the body.
It is possible to find ways to outsource fighting-the-gravity part (i.e. balancing weight fully or partially) to something, so that we can direct our forces in overcoming the inertia as much as possible. Wings represent such an arrangement.

If we bring an aircraft to zero-speed mid-air and stop the engines, it will not have the same downward acceleration as it would have had if it didn't have wings.

So, wings fight gravity on their own (even if they don't get any help from the engine) - to some extent, by using their shape against some properties of the surrounding fluid (air). This is something that engine can't do.

So, a good part of the work done by engine can now be spared from fighting gravity. This is how a thrust-to-weight ratio of less than $1$ can lift the aircraft.

If air was liquid, absolutely no work would be needed by the engine for fighting gravity, and all its thrust could be used for forward movement.
On the other hand, if air had no fluid properties (like pressure etc.), all the fight against gravity would be required to come from engine (thrust $\ge$ weight). An aircraft in air is somewhere in between.

This is somewhat like inclined plane where the plane takes some fighting with gravity (i.e. balances part of the weight), and hence less force than the weight of the body is needed for causing a vertical component of displacement of the body.

While @Floris has answered it in almost totality, I wanted to add one more significant aspect of the wings.

On earth, when we try to generate movement in a body, in general, there are two forces we need to tackle with (ignoring friction etc.) - the inertia of the body and the weight of the body.
The trick is to find ways to outsource fighting-the-gravity part (i.e. balancing weight fully or partially) to something, so that we can direct our forces in overcoming the inertia as much as possible. Wings represent such an arrangement.

A clump of iron would sink in water whereas a saucer of the same weight will not. Similarly, if we bring an aircraft to zero-speed mid-air and stop the engines, it will not have the same downward acceleration as it would have had if it didn't have wings.

So, wings fight gravity on their own (even if they don't get any help from the engine) - to some extent, by using their shape against some properties of the surrounding fluid (air). This is something that engine can't do.

So, a good part of the work done by engine can now be spared from fighting gravity. This is how a thrust-to-weight ratio of less than $1$ can lift the aircraft.

If air was liquid, absolutely no work would be needed by the engine for fighting gravity, and all its thrust could be used for forward movement.
On the other hand, if air had no fluid properties (like pressure etc.), all the fight against gravity would be required to come from engine (thrust $\ge$ weight). An aircraft in air is somewhere in between.

This is somewhat like inclined plane where the rigidity of the body takes some fighting with gravity (i.e. balances part of the weight), and hence less force than the weight of the body is needed for causing a vertical component of displacement of the body.

While @Floris has answered it in almost totality, I wanted to add one more significant aspect of the wings.

On earth, when we try to generate movement in a body (or even to keep the body stable), in general, there are two forces we need to tackle with (ignoring friction etc.) - the inertia of the body and the weight of the body.
The trick is to find ways to outsource fighting-the-gravity part (i.e. balancing weight fully or partially) to something, so that we can direct our forces in overcoming the inertia as much as possible. Wings represent such an arrangement.

A clump of iron would sink in water whereas a saucer of the same weight will not. Similarly, if we bring an aircraft to zero-speed mid-air and stop the engines, it will not have the same downward acceleration as it would have had if it didn't have wings.

So, wings fight gravity on their own (even if they don't get any help from the engine) - to some extent, by using their shape against some properties of the surrounding fluid (air). This is something that engine can't do.

So, a good part of the work done by engine can now be spared from fighting gravity. This is how a thrust-to-weight ratio of less than $1$ can lift the aircraft.

If air was liquid, absolutely no work would be needed by the engine for fighting gravity, and all its thrust could be used for forward movement.
On the other hand, if air had no fluid properties (like pressure etc.), all the fight against gravity would be required to come from engine (thrust $\ge$ weight). An aircraft in air is somewhere in between.

This is somewhat like inclined plane where the rigidity of the body takes some fighting with gravity (i.e. balances part of the weight), and hence less force than the weight of the body is needed for causing a vertical component of displacement of the body.