U.S. Lawmakers Have ‘Grave Concern’ Over Boeing, Airbus Iran Licenses by Reuters @FortuneMagazine September 23, 2016, 11:47 AM EDT E-mail Tweet Facebook Linkedin Share icons Senior Republican U.S. House of Representatives lawmakers made clear on Friday they will keep campaigning against Boeing and Airbus jetliner sales to Iran, despite the Treasury Department’s announcement that it had begun issuing licenses for the exports. Republican Representatives Pete Roskam and Jeb Hensarling wrote to Treasury’s Office of Foreign Assets Control, which oversees sanctions, demanding more answers about any security implications of the delivery of aircraft to Iran. “There is little evidence indicating that Iran Air has indeed stopped transporting weapons, troops, and cash to terrorist groups and rogue regimes,” the congressmen wrote in a letter, dated Thursday, seen by Reuters. Both congressmen hold influential financial positions in the House. Hensarling is chairman of the House Financial Services Committee. Roskam is chairman of the tax-writing Ways & Means Committee’s Oversight subcommittee. Get Data Sheet, Fortune’s technology newsletter. Airbus eadsy and Boeing ba said on Wednesday they had received U.S. Treasury approval to begin exporting over 200 jets to Iran, under a deal struck in January. The news is likely to ease complaints from Iran over implementation of last year’s international nuclear agreement, in which Tehran agreed to curtail its nuclear program in exchange for sanctions relief. Some members of Congress have raised concerns that killing the deal could cost jobs at Boeing plants, but opponents of the deal argue that security concerns are more important. The letter to Adam Szubin, acting under secretary for Terrorism and Financial Intelligence, asked for answers to several detailed questions on issues including Iran Air’s leadership, the Treasury’s ability to control transfers of aircraft or parts once they are in Iran’s hands and the nuclear pact. For more on Boeing, watch: Foreign banks have been reluctant to finance the aircraft deals, fearing they could fall foul of remaining sanctions prohibiting the use of the U.S. financial system for Iranian business. With U.S. Republican presidential candidate Donald Trump strongly critical of the rapprochement, some banks fear they could be left with no insurance if Iran sanctions “snap back.” Republican members of Congress unanimously opposed the nuclear agreement, seen as one of Democratic President Barack Obama’s foreign policy achievements. Arguing that Obama was more concerned with enhancing his legacy than national security, they have pushed legislation and other measures seeking to overturn or undermine the agreement.