pan if you THINK you MAY eat into your reserves
Are we talkin' bout fuel?
Dont you have sops?normally the clever guys do the work so you dont get to guess...
Pan pan if you get too close to min reserve and rather feel unconfortable with any extra delay..ie:you are tossing and turning into your seat.
Mayday if you know you are going to land at reserve level and anything less than a straight in isnt good enough.