The U.S. Army’s whole fleet of around 400 Chinook helicopters has been grounded after fuel leaks sparked a “small number” of engine fires, a spokesperson said Tuesday. The cargo choppers—which became a familiar sight with their distinctive tandem rotors ferrying troops and equipment over the skies of Iraq and Afghanistan—were grounded last weekend. Army spokesperson Cynthia Smith said the cause of the fuel leaks has already been identified and engineers are currently attempting to resolve the issue, adding that some of the helicopters might not even require the fix and could return to service soon. No injuries or deaths were associated with the engine fires, with Smith saying that the Chinooks were grounded out of an abundance of caution.