If I would like to say that one airline stated that there were two flights delay due to an engine failure, should it be “two flight delays”? or “two flights delay”?
One possible scenario
The failed airplane is one of a pair of planes that shuttle between London and Paris. Normally, London-to-Paris flights leave at 8 am, 9 am, 10 am, 11 am, etc. However, due to the malfunction, passengers that were scheduled to be on the 8 am flight are now going to depart at 10 am.
I would call that a two-flights' delay. That is, there was one delay of a duration equal to two flights.
The airplane, while parked at the gate, was discovered to be faulty. Therefore, the passengers on that flight had to be rebooked for a later flight. Furthermore, because it was stuck at the gate, it blocked a second airplane from using the gate at its scheduled time slot, causing the second plane's arrival to be delayed as well.
I would then say that one engine failure caused two flight delays, or that it led to two delayed flights.