Jet2 like all airlines desperately need the cashflow to keep their business alive. While BA might be deemed a strategic asset for the UK, Jet2 management know the Govt will be much less inclined to bail out Jet2. Jet2 management might protest in public but know full well they need to be self-reliant
If Jet2 announce a flight is cancelled, people start demanding refunds and the cash balance in the bank declines rapidly taking Jet2 that bit closer to bankruptcy