Most insectivorous bats work close to vegetation. Tadarida brasiliensis does something else: it climbs. Tracking studies over Texas have recorded foraging bats above 1,000 metres, in some cases considerably higher, exploiting layers where migrating moths are carried on regional winds.
The body suits the job. The wings are long and narrow, giving high aspect ratio and low drag but poor manoeuvrability, which is why free-tailed bats hunt open air rather than clutter. Ground speeds recorded by aircraft-mounted radio tracking have exceeded 100 kilometres per hour, though these figures include tailwind assistance and are not a measure of powered flight speed alone.
The economic angle is often overstated in round numbers. What is well supported is that large colonies consume substantial quantities of agricultural pest moths, including corn earworm; the precise dollar value placed on that service depends heavily on the assumptions of the model used.