Answers are grounded in this paper and cite their sources.
Colin J. Pennycuick, Thomas Alerstam, Bertil Larsson, Soaring Migration of the Common Crane Grus grus Observed by Radar and from an Aircraft, Ornis Scandinavica (Scandinavian Journal of Ornithology), Vol. 10, No. 2 (1979), pp. 241-251
No takes yet. Share an insight, caveat, or question.
Pennycuick et al. (1979) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: