Pilots at the low cost division of BMI, the UK's second largest airline, are being balloted for strike action in a dispute over pay and pensions.
A walkout could hit Bank Holiday passengers
A walkout at BMI Baby could take place around the August bank holiday, one of the busiest periods of the year.
Pilots union BALPA said its members were angry at a 2.4% pay rise.
In a statement, BMI Baby said it remained hopeful pilots would reject the strike call and accept the award all other employees had received.
There are also other separate concerns about pensions contributions for some pilots and the tax free treatment of expenses.
BMI carried 10 million passengers last year.
BBC labour affairs correspondent Stephen Cape said staff in the regional and long haul parts of the company may also join any strike, potentially hitting flights out of London's Heathrow.
Jim McAuslan, general secretary of BALPA, said that at the heart of these disputes was a " total lack of respect" shown by the company towards what he described as its "key people".
"The imposition of the pay increase and the imposition of the higher contribution to the pension scheme, without any meaningful consultations, is a disgrace," he said.
"Taking industrial action, especially around the August Bank Holiday, is the last thing we want but we are driven to it.
"We have tried reason and now we have nowhere else to turn."
BMI confirmed it had been notified by the union of the ballot.
A spokesman said: "This follows the rejection by Balpa of a 2.4% pay award that has been implemented and paid to all other employee and union groups within BMI Group.
"Bmi Baby management remain hopeful that its pilots will reject the ballot and accept the award that all other employees have received."
Bmi Baby employs almost 200 pilots and has an estimated BALPA membership of 140.
It flies from five bases - Cardiff, Nottingham East Midlands, Durham Tees Valley, Birmingham and Manchester - as well as operating one route from Gatwick.
BMI's other services operate from airports including Heathrow, Manchester and Glasgow.