They are mostly fuel and wages of (frequently unionized) employees. For example, numbers for Southwest for the last quarter, of the total $4.2 bil expense:
Fuel: $1.5 bil
Salaries: $1.2 bil
Depreciation + Maintenance: $0.5 bil (basically all airplane related expenses)
So, maintenance expenses are only 12% of the total, while fuel is 35% and salaries 28%.
If the cost of fuel in orbit launches was indeed just 1% of the total cost, then compared to air travel those launches are very inefficient and there may be a huge room for improvement.
Fuel: $1.5 bil
Salaries: $1.2 bil
Depreciation + Maintenance: $0.5 bil (basically all airplane related expenses)
So, maintenance expenses are only 12% of the total, while fuel is 35% and salaries 28%.
If the cost of fuel in orbit launches was indeed just 1% of the total cost, then compared to air travel those launches are very inefficient and there may be a huge room for improvement.