of the most effective things you can do to reduce your carbon footprint
is fly less.
Obviously there are times when flying is more necessary than others. I would never want to ban people from flying to another continent to visit family for example. And sometimes you need to fly for work and some managers are not amenable to arguments against flying. I once worked for an organisation that required us to travel to London occasionally and my environmental argument against flying was not listened to on the time I needed to make the trip. Later though I wished I'd used the tactic of a colleague who claimed that her airsickness was so bad she had to travel by train..... I worked for another organisation that expected staff to travel to Bristol and who actively encouraged people to take the train, and in fact only (officially) allowed flights for people further from Bristol than Newcastle. Edinburgh is further from Bristol than Newcastle but I still took the train ..... If you factor in the time spent travelling to the airport, time spent at the airport and the hassle of airport procedures then for most journeys within the UK, the train is quicker and more comfortable than the plane. Also video conferencing facilities can reduce the need for business travel (while accepting that at least occasionally, actual face to face meetings are important in developing team bonds).
In terms of longer haul flights, the longer the stay in the other country the more you can justify the journey. Flying from Scotland to Paris for a weekend shopping trip is not a good idea, while flying from Scotland to South America to take part in a six month environmental project is more justifiable.
Flying is the fastest growing cause of climate change. If aviation was a country it would be the 7th worst polluter globally. British people apparently fly more than the residents of any other nation. Even if we are environmentally friendly in most of our lifestyle, one flight can completely negate all our other efforts. Technology is being developed to make aviation less damaging but the only way to really reduce the emissions from flying is not to fly in the first place. If it is impossible for you to give up flying completely then you can try to reduce the number of flights you take.
I haven't flown for ten years and haven't flown all that often at all. Though I do wish I'd used the airsickness excuse to get out of a couple of the work flights I took.....
Flight Free UK is a campaign that asks people to pledge not to fly at all in 2020. Their website also gives ideas on how to travel without flying. It's worth bearing in mind though that driving alone in a car isn't environmentally friendly either (though private cars are essential for many people with mobility problems and in rural areas with poor public transport services) and cruise ships are environmentally damaging (though as far as I know ferries are okay - the more basic the ferry the better). We all need to use public transport, ride bikes or walk as much as we can. If you live in an area without decent public transport then you may be able to join a campaign to improve the local bus services.
If you travel by train, coach or ferry you see so much more than if you fly. I've had many lovely birdwatching moments from trains and the ferry journey from Aberdeen to Shetland includes sightings of dolphins and a brief stop at a seabird colony - things that you would entirely miss if you took the plane.