...for certain astronomical applications, due to opacity of even the stratosphere to certain wavelengths. Some observations can be made from high-flying aircraft, but it is my understanding that NASA has decided to cut funding to the Kuiper Airborne Observatory (a large reflector mounted on a commercial jet airliner chassis) in order to "save money". KAO has been flying for years, doing great astronomy and filling the gap between ground-based and LEO observatories. The bugs are worked out of it and it has a big constituency among astronomers.

But it is neither sexy enough to attract voters nor requires huge contractor-friendly development budgets to attract campaign contributors. So it is on the way out.