@simon If you are looking at an overall CO2e budget for the way you live, then in principle you could look at where to allocate that 'spend' of CO2e

In economy a flight is approx 0.13kg CO2e per km flown. Double that for Premium economy and triple it for business class. LHR JFK return in economy is 1.6T CO2e per person.

There's estimates on tinterweb that suggest GPT CO2e at about 24tCO2e per day. Training cost est at 522tCO2e

TL;DR travel is always the big CO2e emission for most of us