Airtightness when sitting in Flight / Control seats.
Airtightness works in a "cockpit" Air vent is showing pressurised space and you can take off helmet etc. If you place a Flight seat / control seat in that space and then sit in it and remove your helmet the space seems to have no oxygen/ pressurisation. Exit the seat and remove your helmet and you are fine. Airtightness fails while sitting in the seats.
And on another note the 1st person view cannot be toggled while sitting in a "Control seat". The work around is to always use a flight seat, this allows you to toggle between 1st person and external camera. The control seat has the 1st person disabled / unavailable.