Mike,

I think that four engine airliners have to be able to fly with two engines
inoperative on one side but I am not certain.


New certification requirements want them to be able to take-off with two out
on the same side at max gross. The A380 for example will have to be able to
do that. The 747 needs three for take-off.

--
Thomas Borchert (EDDH)