The problem is that the tax would need to be super-linear. There are two effects going on.

First, with a fixed quota, the value of a credit is bid up by people wanting to fly, not dissimilar to the Norwegian butter crisis where a stick of butter cost upward of €40.

Second, with a credit transfer system, people selling their credits receive a "negative" tax, while people buying credits pay a positive tax.

This system ensures everyone still has access to a basic level of air travel at today's prices, but is also super-linearly incentivize to travel less.

A linear (fixed) tax on travel will just price out the lowest class, and a linear tax means nothing to those on top of a power-law wealth distribution.