The Ministry of Defence confirmed the military have been on site at London’s Heathrow and Gatwick airports earlier to cover Border Force strikes.
Border Force officers are set to strike from 23-26 and 28-31 December.
Strikes will impact six airports including Manchester and Glasgow.
Armed forces personnel have been training at the airports ahead of the planned strikes.
Hundreds of soldiers were Christmas leave is cancelled.
It is thought about 100 troops are at Gatwick and Heathrow.
Overall, around 600 personnel have been called up to help during the Border Force strikes.
Strikes would cause ‘serious disruption,’ the Home Secretary Suella Braverman warned.
“I really want to urge people to think carefully about their plans because they may well be impacted.”
“If they go ahead with strikes there will be undeniable, serious disruption caused to many thousands.”
