US Black Hawk helicopters in fire-drill foam accident
27 August 2014 Last updated at 12:36 BST
A number of Black Hawk helicopters were left covered in foam after a fire drill went wrong at a US military base in Oklahoma.
The fire alarm system in an aircraft hangar was being tested when fire suppression equipment was triggered - filling the structure with foam and almost burying the nearby helicopters.
No injuries have been reported.
Andrew Humphrey reports.