Special Relativity question Two students, A and B, working in the west (student A) and the east (student B) wings of the research building in Little Rock, AR, simultaneously broke valuable pieces of lab equipment, each producing a flash of light. Their supervisor was on a business trip, flying a super secret jet at the speed v=0.6c, from Charlotte, NC (east) to Los Angeles, CA (west). At the time of the tragic events in the labs, their supervisor was above the research building and saw the flashes of light. Determine the distance between light flashes and time between light flashes as seen by the supervisor, if the distance between labs in the research building is 1400 meters. 
My professor and I are disagreeing about the correct answer to the distance part. I am saying that delta_time has to be zero in the plane's frame of reference to get a proper measurement for the distance, which would give 1400 = gamma*L. This would give a length contraction, which I thought seemed right. But she said that is not the case for this problem because we should consider that the plane would receive the light signals at different times and therefore would measure L=gamma*1400. I don't think that makes sense but we both feel like we are right. Is there some ambiguity in the question or is one of us correct?
 A: The answer depends of what you mean by the "distance between light flashes". If by distance you mean the distance between labs, which assumes that even if the supervisor see the flashes at different times he will correct for the current position of the flash, and measure the two ends of the lab at the same time, then you are correct. But if the distance means the distance between the coordinates of the two flashes even if measured at different times, then your professor is correct. 
A minkowski diagram can easily clarify this:

A: Special relativity questions like this get tricky. IIRC, the proper length is in the frame where both the events happen at the same time. So in this case this is the reference frame of the research building, which is at rest (hypothetically  the Earth isn't rotating here, because if it were technically that would be a noninertial frame!). Therefore, I think your professor is right here, because the two events are the emission of the light flashes, not the supervisor's sight of the two flashes, and those two events happen simultaneously in the reference frame of the research building.
Still, I'm a bit concerned about the equations used here. According to length contraction, if $L$ is the distance between the two events as measured by the supervisor:
$L = \frac{1400}{\gamma}$ meters
