Ryanair would look for an alternative aircraft supplier if U.S. tariffs materially affect the price of planes it has ordered from Boeing, chief executive Michael O’Leary said in a letter on Thursday, adding that he would consider Chinese planemaker COMAC.

“If the US government proceeds with its ill-judged plan to impose tariffs, and if these tariffs materially affect the price of Boeing aircraft exports to Europe, then we would certainly reassess both our current Boeing orders, and the possibility of placing those orders elsewhere,” O’Leary said in a letter to a U.S. lawmaker seen by Reuters.