Qatar awarded a contract for up to 210 new wide-body civilian airliners to Boeing on Wednesday, a blockbuster deal for the beleaguered aerospace company that was inked in a Doha ceremony where President Donald Trump hailed it as evidence of his abilities to promote U.

Trump is headed to the Middle East for his first major foreign trip in his second term.

Democrats on the Senate Foreign Relations Committee said Trump’s acceptance of the plane would create “a clear conflict of interest, raises serious national security questions, invites foreign influe...