1. The global increase in light pollution is being viewed with growing concern, as it has been reported to have negative effects ranging from the individual to the ecosystem level.

2. Unlike movement on the ground, flying and swimming allows vertical motion. Here, we demonstrate flight altitude change is crucial to the perception and susceptibility of artificial light at night of airborne organisms. Because airborne species can propagate through the airspace and easily across ecotones, effects might not be small-scale. Therefore, we propose including airspace as a vital habitat in the concept of ecological light pollution.

3. The interplay between flight altitude and the effects of light pollution may not only be crucial for understanding flying species but may also provide valuable insights into the mechanisms of responses to artificial light at night in general.

The digital camera images were taken by Canon EOS 6D camera at the four principal directions and the zenith. Camera settings: ISO 6400, f/3.5, 30s exposure time. The images were processed by the author"s DiCaLum software (dicalum.eu)

The spectra (ksee_spectrum1.d and ksee_spectrum2.d) were measured by a Konica-Minolta CS-2000A spectroradiometer. The nightly data were averaged to reduce measurement noise.

Most image processing and viewer software can open Canon CR2 files (e.g. gimp, dcraw).

Any plotting program or text editor opens the spectral data. We provide a CC0 license-compatible simple Gnuplot script (ksee_spectra.plt) that we used to make the figure. Gnuplot is an open-source plotting software.