The authors of “A Fast Adaptive-Gain Complementary Filter Algorithm for Attitude Estimation of an Unmanned Aerial Vehicle” first published online on 21 May 2018 (Yang et al., Reference Yang, Sun and Yang2018) have drawn attention to the fact that some of the work insufficiently acknowledges the work of Wu et al. (Reference Wu, Zhou, Chen, Fourati and Li2016). Section 2.2 of Yang et al. (Reference Yang, Sun and Yang2018) builds on the work of Wu et al. (Reference Wu, Zhou, Chen, Fourati and Li2016).

In Yang et al. (Reference Yang, Sun and Yang2018), the authors derive an observation model of attitude quaternions from normalised accelerometer measurements. The method of Yang et al. builds up the linear measurement model via Taylor approximations. Some significant contributions and new filter designs are shown in this paper which deal with the problem of adaptive estimation. Regarding the factorization of the direction cosine matrix, it has been systematically described in Wu et al. (Reference Wu, Zhou, Gao, Li and Fourati2018), but this has not been noticed by Yang et al. as this paper was published after the original submission of Yang et al. (Reference Yang, Sun and Yang2018). Yang et al. (Reference Yang, Sun and Yang2018) uses different compositions of a dynamical system that achieves the same result as in Wu et al. (Reference Wu, Zhou, Chen, Fourati and Li2016).

Yang et al. would like to apologise to Wu et al. and the editorial board of the Journal of Navigation for their failure to properly cite the earlier work and acknowledge the originality of Wu et al.'s work.