Whilst the argument I can't fly more than one so you can't drive more than once may sound reasonable there's a few issues with it.
If I drive 610 miles that's the same as one return flight to Paris, however the rest of my family travel for just the emissions of one person flying. Therefore based on personal emission levels we could make that trip for each of us rather than us each make that flight.
That's before high altitude emissions have a larger impact than those at ground level - partly due to the water vapour emissions which also impact climate change.
I can assure you that my kids are made to walk to school (even when it's raining) and we put our washing outside as much as possible (we do have a tumble dryer but don't want to use it without good reason - having a family does make trying to dry all our washing within our house rather difficult and would likely require us to use for heating far more and probably would be worse than using the tumble dryer the limited amount of time that we do).
Between my wife and I travel the same (or less) number of average miles by car as two people's total travel (13,000 miles), however that means that as a family we've still got our children's milage to cover the walking/cycling that we do.
However our driving distance includes those above average numbers of "holidays" that we take to see family - which means that if individually we were permitted a return flight to Paris we could actually go on holiday again - so thanks for that.
I'd be quite happy to have a personal carbon budget which I could trade my households under use with those who wanted to use more. I reason that I could do rather nicely or of such a scheme - I do however fear that you may well find it rather expensive.
IF there were limits on the number of flights an individual could do without paying an extra amount, I would suggest a value of 8 flights (so 4 return trips). Then it would increase the APD by a factor of 1.5 for every 2 additional trips you make (applied to the cheapest rate first). Except for flights where there was a train option which took under 4 hours where APD would be triple the starting rate (£19.50 for a domestic flight rather than £6.50).
For way of justification for the 8 flights; that would allow for every single air passenger on flights at UK airports to be half of the UK residents. Even though quite a few of those will be people with other nationalities, so clearly anyone flying now than that is way above the national average.
By applying the doubling to the lowest rates, people (even if they couldn't claim back the extra APD from their company) could still do a decent long haul flight to see family even if they did a lot of business travel.
For someone doing 20 flights a year (2.5 times the number of flights before APD starts to rise) the extra cost could be as little as £810 (all domestic flights in economy) but could be as high as £5,034 (all ultra long haul in premium cabins).
Before anyone thinks that's a lot, it should be considered just how much that individual would be paying in air fares to undertake 10 return trips in business or first class. As it could easily be £2,500 for each return trip, which could put the ticket prices paid at £25,000, meaning an effective tax rate of 21%.
Very few people would be flying for work ultra long haul more frequently than once every 5 weeks and if they are costs would start to track up fairly quickly (24 flights would put the upper tax at an extra £13,177).
Arguably businesses shouldn't be relying on one person that much, or if does then there'll be a significant risk to that company if that person no longer worked for the organisation and it's questionable as to whether that business should carry on operating in that manner.
Yes, of course, business will start to look at making short hops and then connecting to the long haul destination from there, but no more than normal for the first 8 flights and unless the connections are reasonable maybe not even for the next few flights (12 flights would max out at £350 extra).
It's fairly unlikely that individuals would travel to (say) Australia more than twice in one year, and fairly few would travel to Europe more than four times. Even then eight trips to Europe would cost them an extra £213, so whilst it may stop them from going (say) every month, it still would be quite a few times in a year.
Over time it could well be that the APD rises and/or the number of flights without an extra charge reduce to nudge people towards fewer flights, however that's how I'd suggest that it would run IF such a proposal were to come forwards. As it would be a fairly reasonable balance between don't something and doing nothing.
The frequent flyer levy along with banning point to point ticket sales for journeys with acceptable train journey times are good ideas. I like them in principle but fear they are they would be "the thin end of the wedge." This thread demonstrates there are people who want to ban all non electric flying as soon as possible.