A health and safety investigation is under way at Heathrow's Terminal 5 site after the death of a civil engineer from Devon.
The pair were working on a car park at the new T5 terminal
Matthew Gilbert, 27, from Plymouth, died on Wednesday after falling from where he was working on the construction of a car park.
Another worker is in a serious condition in London's Charing Cross Hospital following the accident.
Other workers at the west London site went home on Thursday out of respect.
Both men were employed by Laing O'Rourke and were working on the construction of a new multi-storey car park at the western end of the site when they fell.
They were both given urgent treatment at the scene by the on-site medical team as well as emergency services.
Work was suspended in the area where the accident happened and a Health and Safety Executive investigation is being held.
T5 managing director Tony Douglas said: "I am deeply shocked and saddened by this tragic accident, and on behalf of the whole T5 workforce wish to send our condolences to Mathew's family and friends.
"Thorough investigations into exactly what happened are under way and we are determined to understand the cause as quickly as possible."
Laing O'Rourke chairman Ray O'Rourke said: "This is a dreadful event and our thoughts are with the family and friends of both men.
"We take the safety of our workforce extremely seriously and we have initiated an immediate investigation.
"We are offering our full support and co-operation to the Health and Safety Executive. However, it is too early to speculate as to the cause of this tragic accident."