  In this paper, we describe the outcomes of the challenge organized and run by
Airbus and partners in 2018. The challenge consisted of two tasks applied to
Air Traffic Control (ATC) speech in English: 1) automatic speech-to-text
transcription, 2) call sign detection (CSD). The registered participants were
provided with 40 hours of speech along with manual transcriptions. Twenty-two
teams submitted predictions on a five hour evaluation set. ATC speech
processing is challenging for several reasons: high speech rate,
foreign-accented speech with a great diversity of accents, noisy communication
channels. The best ranked team achieved a 7.62% Word Error Rate and a 82.41%
CSD F1-score. Transcribing pilots' speech was found to be twice as harder as
controllers' speech. Remaining issues towards solving ATC ASR are also
discussed.
