Both Ryanair and IAG are facing fresh threats of strike action by their British-based pilots.
The trade union representing airline pilots in the UK - the British Airline Pilots' Association (BALPA) - is entering talks with Ryanair on the back of the airline's British pilots signalling strong support for industrial action over pay and working conditions in an indicative ballot.
Ryanair suffered a series of damaging strikes last year after the airline bowed to pressure in late 2017 to recognise unions for the first time.
That contributed to the airline's weakest annual profit in four years.
IAG is facing the same threat as British Airways pilots have called for a strike ballot after the rejection of BA's latest pay offer.
IAG also owns Aer Lingus and Spanish carriers Iberia and Vueling.
Ryanair's share price rose marginally despite the strike suggestion, but IAG fell slightly.
Ryanair, meanwhile, has accelerated its push to reshape its group structure - to more resemble that of IAG with a number of subsidiary airlines - by agreeing to purchase start-up airline Malta Air.
It adds to its Ryanair, Buzz and Lauda airlines.
Ryanair will move its six Malta-based aircraft into the Malta Air subsidiary.
It plans to grow that fleet to 10 within three years and create more than 350 jobs.
Malta's tourism minister Konrad Mizzi said the country's relationship with Ryanair is now "a successful collaboration", which will contribute "in a large way" to the country's development.