Seventeen thousand flights have been cancelled in Europe alone, costing airlines at least $200 million a day. US medevac flights from Iraq and Afghanistan can't land at military hospitals in Germany.
FedEx is re-routing planes and travelers are scrambling for alternatives on the ground. The airports in Geneva and Vienna have shut down.
London's Heathrow won't reopen for flights until at least tomorrow. And the backup could get much worse.
"We are going to be very conservative and make sure the air is really clear before we start launching flights into it," President and CEO of Flight Safety Foundation Bill Voss said.
In Europe, air carriers are booking hotel rooms for stranded travelers. But under US law, airlines do not have to provide meals or hotels.
The flight problems have led delegations from several countries to cancel their plans to attend the state funeral for the polish president and his wife on Sunday.
The two were killed along with nearly one hundred other people last Saturday when their plane crashed in western Russia.
President Obama still plans to attend the funeral service Sunday.