Laing O'Rourke workers at Heathrow have begun a three-day strike over bonus payments.
Over 900 T5 workers started a three-day strike this morning over a bonus dispute.
The Laing O'Rourke workers at Heathrow are demanding an extra £1 an hour in bonus payments. The company had offered 67p, but this was rejected in a ballot last week.
It is believed that officials from GMB, T&G and Ucatt also rejected an 80p offer made late last night.
Picket lines have been set up around the site. The strike is the third on the site to affect the sector. It follows the award of a £1 an hour bonus to electrical and steel sectors last year.