Phileas, did you read my post? I know that not many people live in central Carlisle, in the same way very few people live in the centre of London.
If you don't live in the centre then you need to drive to the centre with the morning rush or drive to the airport which is going against the traffic. Eitherway, you have to drive there. Forget public transport, outside of London it is too infrequent to be relied upon and anyone who has lived in the lakes (first hand experience here) will have a car.
Carlisle airport, possibly 2 flights departing together, it's an LCY-style operation, so of course you can rock up 30 mins before, no problem. In fact it will be one of their major selling points I am sure.
Your anxiety over traffic and delays etc applies equally to the train and as has been pointed out, these days everyone knows the restrictions on liquids. By the way, if you've flown recently you will know you CAN take them through security, you just have to pop them into a little clear bag.
The flight WILL take less than an hour. The transfer to the train WILL take a maximum of 20 mins (I'll let you have the 5 minutes), the train to London WILL take 50 minutes. So from arriving at the airport to stepping onto the Liverpool Street platform will take 2hr40 mins. The train DOES take 4hrs + 15 mins to arrive and collect tickets etc. Most people will probably arrive with 30 mins to spare.
So even if you fanny around for half an hour, you're still going to get to your destination at least an hour or more quicker if travelling by plane.
It is known that for a rail journey of less than 3 hours, train is quicker, that's obvious, but when you are talking >4 hours, the flight starts to look very appealing, especially if you can travel secondary airport to secondary airport and avoid the big hubs.
Sorry if I don't agree with you mr Fogg, but i used to travel regularly on the 0700 shuttle from Manchester to Heathrow and was always in central london happily by 9 in the days before the Heathrow express. If you can do it from MAN and LHR with long walks and busy airports, I am damn sure you can manage it from CAX to SEN