In a brief statement, the US military said the two Marine Corps aircraft were flying in support of operations when contact was lost.
It said there was no indication of hostile fire in the area at the time. A search effort is under way.
US media quoted naval officials as saying they thought the two planes had been involved in a mid-air collision in bad weather.
The planes were from the USS Carl Vinson aircraft carrier.
F/A-18 jets have different versions, one flown by a single pilot and the other carrying two crew members.
It is not clear which type of plane was involved.
http://news.bbc.co.uk/2/hi/middle_east/4507609.stm
Those things are not cheap
