My wife, a crewmember working for a European company, needed a Schengen visa for all entries into Schengen-states while working outside the said states. After we moved back to Europe, she got stamped on every trip in and out of schengen. UK did not require a visa for flights arriving as crew (on Gendeck).
My current employer also employes many non-EU citizens some with UK residence permit some with none. They all require a visa for entry in Schengen countries with passports checked and more or less regualrly, stamped for entry and exit. Working for a company with only tech stops not having a visa would not be a problem, unless your current citizenship is on the list that requires you to have a visa crew or not.