JAL roundtrip from Chicago to Tokyo last week. I could not believe the 777-300ER had no individual ventilation system per seat. Whatever the reason the result is that the economy section was extraordinarily hot and stuffy where my daughter and I were sitting - to the point where she got sick and had a mild asthma attack. For 12 hours I was sweating with no relief. The return plane was a bit better but very uneven. It would cool down only to get hot again for 45 minute stretches. Several passengers including myself complained about the poor ventilation and A/C. I walked all over the economy section and noticed that as I walked down an aisle I could literally feel the temperature change - the uneven cooling was that noticeable. JAL flight attendants heading to Narita were very sweet to my daughter who had to sit in the jump seat in the galley as it was significantly cooler. On the way back to Chicago the flight attendant I complained to who was serving our side of the economy section was rather argumentative saying some passengers complained they were cold and had extra blankets. Well hardly anyone in economy had them as it was easy to check. I called her out and asked her to prove this and then she shut up. I happened to casually chat with 3 other passengers on this leg who also complained about the atrocious ventilation/temperature. What is going on here? JAL's food is pretty bad and the section is cramped but I got what I paid for so no complaints. They were very efficient in their service all around even if the food was awful and the red wine I got had actually turned into vinegar. I shall never fly them again.