There are currently around 17,000 aircraft parked up at airports around the world, according to consultants Ascend by Cirium. That represents about two-thirds of the global fleet.The real problem, executives say, is the number of different countries that have introduced travel restrictions, and the lack of certainty over when those restrictions will be removed. Domestic routes within individual countries will open up first, followed by short-haul international services. Intercontinental travel would probably follow after that.