The good news about WindJet is that the flights are cheap, and they fly good aircraft. The bad news is that you're likely to get socked with excess baggage charges if your luggage weighs more than 15 kg.

The tickets were just 43 euros each for our flight from Palermo to Rome, but my son's suitcase was 23 kg. We were charged 8 euros per kg for a total of 64 euros.

What really frosted me was that I saw lots of people in the line ahead of us schlepping bags that appeared bigger and heavier than my son's, but not one of them was sent off to the distant window elsewhere in the airport to pay the extra charges.

The weight limits are printed on the ticket I booked over the Internet. So, the airline had the right to zap us. However, it appeared that not one Italian in the line ahead of us got socked with these charges. Though I have an Italian surname and speak the language, it seems to me we were singled out because we were Americans. I wrote to WindJet after we returned but, a week later, have received no reply.

So, if you plan to use WindJet, make sure each bag is within the 15 kg limit for domestic flights in Italy.

Curious. Did you buy your tickets in Italy or before you left home?

Thank you for the heads up - it's helpful to get reminders like this about excess baggage charges. I'm not sure I understand your complaint, however.

Did you actually weigh the bags of the people in front of you or is it mere conjecture that they weighed more than 15kg?

Why do you say the airline zapped you? You were informed ahead of time of the 15kg limit yet you chose to pack a bag that was nearly 18 pounds over their limit. That was your choice to make.

What remedy do you expect from WindJet? When you purchased the ticket you agreed to the terms, and yet now you're complaining that they should change the rules for you.

What am I missing here?

I bought the tickets online while in the US.

My "complaint" is that the rule was applied selectively. I saw numerous individuals with large suitcases and duffel bags who were not charged anything extra. Of course, I could not see the scale. But we watched a long line of people get processed for the previous in-country flight, and not one was sent off to the office to pay extra charges. The people in that line were mostly Italian; we're American.
To my eyes, the evidence suggested we had been singled out.

Just because a suitcase is large does not means that is heavier than a smaller one.