The alleged attacker, Hamam al-Hammami, had been banned from flying with Oman Air because of concerns about his radical views, a person familiar with the matter said.
The African nation refused to make an agreement with the Trump administration, which has sought to slash foreign assistance and impose new terms on recipients.
Secretary of State Marco Rubio will visit friendly governments in Colombia, Ecuador and Peru. But his support for the Venezuela oil deal is rankling some in the region.