TfL should withdraw the early morning buses that serve the airport if the subsidy is removed. the first
490/482 gets to Heathrow Terminal 5 at 04:00 ish. no way that running buses that early is profitable . When in the case of the 482 it can bearly sustain a 20 minute frequency throughout the day anyway pre covid and demand to terminal 4 is now non existent.
Heathrow would soon change its tune if it's employees can no longer get to work.
There has been a consistent attempt by Heathrow Airport limited to nickel and dime TfL over both crossrail contribution costs and track access fees for the service.
I suspect that this is in part motivated by spite caused by successful legal challenges to the third runway, failed attempts to charge high track access fees for crossrail and iirc the free travel zone was in part one of the conditions attached to ensure the construction of terminal 5.