Heathrow airport and airline managers warn that proposals for the Tube to run later on Fridays and Saturdays could have a negative impact on the airport.
The Tube would open an hour later on Saturdays and Sundays
Managers for airport operator BAA and British Airways say staff would struggle getting in for early shifts.
A later-running Tube - until 0200 GMT - means trains would start at 0700 GMT on Saturdays and at 0830 GMT on Sundays.
Transport for London (TfL) said the number of people at the airport affected by the proposals is small.
A TfL spokesperson said: "Previous TfL research has shown that 140,000 passengers would benefit from a later running Tube and 55,000 would be affected by it opening an hour later, a small percentage of which would be travelling to Heathrow airport.
"It is important for Londoners to understand that if the Tube runs later, it will need to open later on Saturday and Sunday so that essential engineering work can be carried out."
TfL said no decision had yet been made for trains to run later at the weekend and it hoped to get the views of all affected Londoners.
The consultation period ends on 22 April.
A BAA spokesperson said: "We have some concerns about the proposed plans and the impact they will have on people, particularly staff, who need to get to the airport early in the morning."
He said the company is consulting with London Underground on their current proposals and will be responding formally.
A spokesperson for BA, which also opposes the late opening of the Tube, said: "At a time, when staff and passengers are being encouraged to use public transport to travel to Heathrow it is very unfortunate that obstacles are being put in their way."
Both BA and BAA are encouraging staff who would be affected by the changes to air their views by writing to TfL.