Air travel

We are traveling from Newark to Los Angeles by plane with our 4 month old male. I purchased a Sherpa Bag for travel, size medium. He will fit in the seat in front of us. Our flight is nonstop, so total travel time will be about 7 hours. Our vet said that she cannot prescribe any medication to calm him because it will lower his blood pressure, and therefore his overall resistance, too much. Would anyone suggest giving a 4 month old a very mild sedative for an airplane flight?