It's very easy to run emergency backup generators in parallel.
Take your total load (10MW) divide by 5 (2MW) and you need 5 2MW generators, buy 7 and run 6/7 and your "down for yearly maintenance" generator can be offline while your "oh shit we installed the wrong fuel filter and the injectors clogged" generator also fails.
Especially since rarely does anyone care about how heavy the emergency generators are. But if you add 100 lbs too much in the wrong place on a GA plane, everyone is almost certainly going to die.
Take your total load (10MW) divide by 5 (2MW) and you need 5 2MW generators, buy 7 and run 6/7 and your "down for yearly maintenance" generator can be offline while your "oh shit we installed the wrong fuel filter and the injectors clogged" generator also fails.
Much harder in a plane.