The results of making a six-hour flight a nonsmoking flight are absolutely predictable as evidenced by the TWA incident. It is unrealistic to expect anything except flaring tempers, illegal smoking in restrooms and in-flight fires.
To ask regular smokers to abstain that long is like requiring a diabetic to miss his or her insulin shot. It just isn't reasonable.
Segregation is a far better answer. If there is one row of smokers on the plane, then the back row should be designated a smoking area and passengers rearranged to accommodate the needs of both smokers and nonsmokers. To do otherwise endangers all of us.