Two US airmen were listed as missing on Tuesday after their F-15E warplane went down in Iraq on Sunday.
The two men and their aircraft, known as a Strike Eagle, were deployed from the 4th Fighter Wing, Seymour Johnson Air Force Base in North Carolina, the US Defense Department said in a statement in Washington.
The cause of the incident was under investigation, the statement said, but it provided no details of any search and rescue operations.
It added a note of warning to Iraq.
"The (US-led) coalition expects Iraqi forces and Iraqi citizens to abide by all Geneva Conventions relating to the treatment of prisoners. Violations of these laws will bring swift and severe consequences," the statement said.
The two airmen were among the 10 listed as missing on the Pentagon's casualties list. So far, 96 US military personnel have been killed and seven listed as prisoners of war.
Earlier on Tuesday, a US A-10 Warthog ground attack fighter was shot down near Baghdad airport, but the pilot was safely rescued, officials at Central Command war headquarters in Qatar had said.
