hi welcome to the forum ............... hmmmm the only thing i can think of is, you're getting the "mission failed - too long" message is the aircraft that you're escorting has been shot down!!!!
at the start its a free for all and when you have to "escort" there will be a blue triangle that flashes, order you're flight to form up on you double down on the "d-pad", find the blue target (it will be getting harrased by 109's over the coastline) select a couple of targets once you've you have found the aircraft you're looking for you're flight will help you shot the enemy aircraft
hope's this is of any help and if im wrong someone correct me lol
many thanks scotty