You’d think a giant company that buys planes would have a half-decent relationship with a giant company that makes planes. And, for the most part, Delta and Boeing have been business buddies over the years. But now, these two big guns of American aviation are lined up on opposite sides of one of the biggest policy fights rocking Congress: The debate over the Export-Import bank.

Big companies tend to get their way in Washington because opponents are usually weak. Think Wall Street versus Main Street, or cable companies against subscribers. Those aren’t real boxing matches, they’re more like Mike Tyson fighting your Uncle Stewart. But Boeing versus Delta is a real matchup, and it has observers in politics and business riveted.

Among other things, the Ex-Im bank uses American tax money to help foreign airlines buy Boeing planes. Those airlines are Delta’s competitors, and Delta doesn’t like the idea of American money going to them. Recently Delta’s CEO testified on Capitol Hill, flanked by uniformed pilots and flight attendants, to say this practice should stop.

Boeing says the Ex-Im Bank helps Boeing compete internationally and create more American jobs. And the company has benefited for a long time from the Ex-Im Bank’s support. But now, with Delta in the ring and Ex-Im Bank skeptics gaining power in Congress, Boeing’s long and cushy ride with the Bank is encountering some turbulence.