Boeing's plan to sell aircraft to Iran is experiencing bipartisan turbulence on Capitol Hill.

A number of House Democrats joined their Republican colleagues July 7 in expressing support for setting conditions before the manufacturing giant can proceed with its $17.6 billion deal to sell 80 passenger aircraft to Iran Air. The Obama administration insists it has the tools to ensure that any planes won't be diverted to unapproved purposes, but lawmakers of both parties are showing an interest in requiring Iran to meet certain criteria before the Treasury Department approves any sale.

"We're being asked to transfer planes to a company, Iran Air, that has served as an air force for terrorism. And we're being told, oh, but just trust them, or just trust that we'll be able to do something if they violate," Rep. Brad Sherman, D-Calif., said at a hearing of the Financial Services Committee's trade panel. "When Iran comes forward with a plan to guarantee that these planes are not being used for terrorism or to support [Bashar al-] Assad [in Syria], then we could consider [granting export licenses]."

While Sherman opposed the nuclear deal that paved the way for the Boeing sale, several supporters also raised concerns.