By now, frequent travellers are painfully aware of the $25-to-$75 fee most US airlines charge for the first and/or second piece of “normal” checked luggage – meaning the bag has to weigh less than 50lb.

But it’s the excruciatingly high fees airlines charge for overweight pieces of luggage that now surprise and frustrate travellers.

On US flights, the normal checked bag fee nearly triples ($50 to $100 each way) if the bag weighs more than 50lb. Even Southwest Airlines, famous for not charging fees for the first or second checked bag, charges $50 for overweight bags.

If you go over the 70lb limit on international flights, well, the sky seems to be the limit. Last month, some US airlines began charging an astonishing $400 to $450 fee each way for international checked baggage weighing between 71lb and 100lb.

While most non-US carriers allow passengers to check one or two bags on international flights without charge, fees do come into play for heavy bags. Lufthansa, for example, charges 50 to 300 euros for overweight bags.

Here are five tips to avoid getting hit with a fee that may amount to more than the fare you paid:

Weigh your empty bag.
Leather luggage might look classy, but it’s very heavy — some standard-sized bags can weigh up to 20lb — empty!

Invest in lightweight luggage
There’s a new generation of luggage made from tough composite materials. For example, Samsonite recently introduced an ultra-light line of luggage made with what it calls CURV technology. Standard upright suitcases with wheels weigh in at as little as 5lb.

Weigh your packed bag before arriving at the airport
If you are checking more than one bag, spread the weight between the bags to keep them under the limit.

Put your heaviest items in your carry on bag
Some airlines don’t impose weight limits on carry on luggage. Here's a helpful chart showing which do and don't (in the US).

Wear your heaviest clothing on the plane
Don’t pack those heavy boots or coats, wear them instead.

Chris McGinnis is the business travel columnist for BBC Travel

Correction: A previous version of this article stated that airlines do not impose weight limits for carry on luggage. This has been fixed.