I was on a flight recently where my flight was schedule for 5:50PM, but when I got to the gate, the time had changed to 5:45PM and eventually 5:40PM. While it didn't make much difference for me since I was there early, that 10 minutes could be someone making and missing their flight.
Are airlines allowed to make flights leave sooner? If someone misses their flight because of this, do they have to be compensated by the airline?