I think all international flights are all inclusive, but it pays to double check on domestic flights, especially in the US. I got stung on a flight last summer between Chicago and Seattle - about a four hour flight, I guess, but food was not included and you had to buy either a sandwich type meal (I think it was $7) or a "snack pack" (which was $5). Having been out of the states for two years, I didn't know about this little change in service. Travelling with four little kids, I was kind of irritated when I discovered this, but the worst was when the attendant came around asking for my order and then informed me that YOU HAVE TO PAY CASH. That was when I discovered that I had less than $5 in my wallet (why would you need cash in flight? You can hit a machine at the airport when you land!) but fortunately my daughter had a little change and we managed to scrape up enough for one snack pack. To split between the five of us.
Live and learn, and share your knowledge!