Qantas is planning to lift domestic capacity from next April, but analysts are warning the additional flights will do little to take the sting out of steepling domestic airfares that jumped to fresh heights in the first weeks of December.

The average cheapest available fare between Melbourne and Sydney is $268, Bureau of Infrastructure Transport and Regional Economics (BITRE) data released on Thursday shows, up from $161 in November. This jump is more severe than the national average, which was up 14 per cent month-to-month.