Obama and Biden joined Secretary of State Hillary Rodham Clinton and Secretary of Defense Leon Panetta to express condolences in a private waiting area at the Andrews Air Force Base terminal.
Obama and his dignitaries were at Andrews to witness the transfer of remains ceremony for Ambassador Chris Stevens and three others killed Tuesday in Benghazi.
Also killed were Americans Sean Smith, Glen A. Doherty and Tyrone S. Woods. Doherty and Woods were former Navy SEALS.
U.S. officials are investigating whether the assault was a coordinated terrorist attack that took advantage of protests in the Arab world over an anti-Muslim video.