We all sound fairly critical of the u-flak idea, but don't forget that we're benefiting from hindsight.
If you can imagine, the Germans must have simply sent out u-boats from their pens and, two or three days later, realise that they weren't answering radio calls anymore. I suppose (educated guesswork - no source for this) that they had to run u-flak before they even realised that the allies were patrolling with two or more aircraft together. I guess that when a solitary u-boat was found, attacked and sunk, the crew had more pressing things to do than radio out detailing how many aircraft were actually doing the attacking; especially when such messages required Enigma encryption.
If the Axis were under the impression that allied aircraft patrolled individually to cover more ocean, u-flak escorts probably didn't seem like such a bad idea. Remember also that the boats would have been converted/ordered well before the first saw combat.
Just a 'devil's advocat' point!
