Ah, eagle - is it the pic of the Lynx that upset you? Fear not - that was a fully legal and authorised manoeuvre back in the days when 1 BR Corps and attendant flying types were poised to throw Boris back east of Berlin. The skill was practised to enable the anti-tank helis to move in and out of firing position without exposure to enemy view/countermeasures. All other battlefield helis practised the same task to enable them to operate in the NW European likely-conflict area.
Flight under wires is still practised; there have been operations which have required the technique - not everywhere has the cosy punch-up-to-MSA and recover for an ILS option.
Just 'cos people had to do it doesn't mean to say they couldn't enjoy it, though, eh?