U.S. airlines collected more than $6 billion in baggage and reservation change fees from passengers last year — the highest amount since the fees became common five years ago.

These fees — along with charges for boarding early or picking prime seats — have helped return the industry to profitability.

Airlines started charging for a first checked suitcase in 2008 and the fees have climbed since. Airlines typically charge $25 each way for the first checked bag, $35 for the second bag and then various extra amounts for overweight or oversized bags.

The nation’s 15 largest carriers collected a combined $3.5 billion in bag fees in 2012, up 3.8 percent from 2011, according to the Bureau of Transportation Statistics. Reservation change fees totaled $2.6 billion, up 7.3 percent.

The airlines took in $159.5 billion in revenue last year and had expenses of $153.6 billion, according to the government. That 3.7 percent profit margin comes entirely from the baggage and change fees.

Passengers likely won’t get relief from the fees anytime soon. American Airlines, Delta Airlines, United Airlines and US Airways all recently raised the fee for changing a domestic-flight reservation from $150 to $200.

Even Southwest Airlines, which promotes its lack of change fees and “bags fly free” policy, recently announced a new policy on noshows. Passengers who buy the cheapest tickets will have to cancel a reservation before departure; otherwise they won’t be able to apply credit from the missed flight toward a later trip.