Firestorm
I very rarely swear on these forums but you're talking crap & on very dodgy ground by implying withdrawal of AOC.
Jet2 has a number of aircraft from outside operating for them this summer because they know they can't crew the duties required as it stands. In order to be able to comply with EU261, Jet2 has a number of crews on Airport Standby throughout the network from 0500z-2000z in addition to units based in mainland Europe that can get pax to/from their destinations with minimal delay. All these extra duties require extra crews as coverage.
Also Jet2 has recruited mainly B737 F/O's to replace FO's that have been promoted to crew the extra aircraft they've bought & some that have left the firm. In addition to those crews, Jet2 will be redeploying the GLA & EMA B757s to NCL, LBA & MAN over the next couple of years, replacing them with B737NG's. The B757 crews based at GLA & EMA were offered either a base transfer or fleet transfer. Most opted to transfer to the B737NG fleet & stay at their home bases. Some opted to stay on the B757. I think Jet2 are getting at least 4 more airframes over the next 12 months.
So lots of recruitment & lots of training to fuel Jet2's steady expansion.