Thousands of workers at British airports including Gatwick and Heathrow are to vote on strike action in the next few weeks.
Stansted could be one of the airports affected by strike action
BAA staff are to be balloted on strike action in protest at a plan to stop new staff joining the final salary scheme from 1 December.
A strike could see BAA airports closed from 27 December, leading to chaos during the New Year travel period.
The ballot will take place from 29 November.
"It is clear that the pension scheme is financially sound and should be left alone," said union officer Brendan Gold.
A spokesman for BAA said that the company "regrets the union's threat of industrial action, particularly in the Christmas period.
"We believe the way to resolve this is through negotiation," he said.
Low-cost airline Easyjet said it would be speaking to BAA "to ensure contingency measures are in place to ensure our operations are not affected in the event this goes ahead".
Budget airline Ryanair expects BAA to have "an appropriate contingency plan in place" in the event of a strike.
"This [the strike] is entirely a matter for the BAA," a Ryanair spokesman added.
Virgin urged both sides to work hard to resolve the dispute so that passengers did not face industrial action at such a busy time of the year.
Unite union represents 5,000 airport workers employed by BAA.
They include firefighters, security, maintenance and administration staff at airports from Aberdeen to Southampton, including some of the UK's busiest - Heathrow, Stansted and Gatwick.
Virtually all firefighters at BAA airports are union members, the union said.
A strike by firefighters could see airports close, the union said.