50 45. It is also beneficial if each deportation operation where difficulties are foreseeable is monitored by a manager from the competent unit, able to interrupt the operation at any time. In some of the countries visited, the CPT found that there were spot checks, both during preparations for deportation and during boarding, by members of internal police supervisory bodies. What is more, in an admittedly limited number of cases, members of the supervisory bodies boarded aircraft incognito and thus monitored the deportee and the escort until arrival at the destination. The CPT can only welcome these initiatives, which are all too rare at present in Europe. Further, the CPT wishes to stress the role to be played by external supervisory (including judicial) authorities, whether national or international, in the prevention of ill-treatment during deportation operations. These authorities should keep a close watch on all developments in this respect, with particular regard to the use of force and means of restraint and the protection of the fundamental rights of persons deported by air.