Heathrow and Gatwick airports have said they are monitoring porous concrete found on their sites after school closures linked to the material.
The airports had previously found the reinforced autoclaved aerated concrete (Raac) before extensive news coverage over its use.
Heathrow said it had the means to keep it safe until it can put “permanent solutions” in place.
Gatwick said it has found no cause for concern.
The discovery of the concrete, which can crumble, in schools and public buildings has led to a number of closures since the start of September.
The material was discovered at Heathrow Terminal 3 last year, and the airport has put measures in place to make it safe.
Since the Raac concrete was found at Heathrow, the airport has reviewed its management plans and is satisfied with them.
A Heathrow spokesperson said the airport had been “assessing our estate and will continue to mitigate the risk where this material is found”.
Gatwick has carried out regular inspections on the concrete and is not worried about its findings.
A Gatwick spokesperson said: “We have a register of locations containing Raac on the airport campus, which are closely monitored through a regular comprehensive structural inspection regime.”
The most recent Gatwick inspection was in June, and “did not present any concerns”.
Gatwick will continue to monitor the Raac on a regular basis, the spokesperson added.
A spokesman for Manchester Airport said regular inspections had found no Raac on site, and the airport was running another inspection to double-check.