I need help this week i have to travel by the plane for 10 hours. how many mg of klonopin (clonazepam) should i take before i get on the plane?

Depends: Even 1/2 of 0.5 mg pill may be enough if you have not been taking it on a regular basis. If you have been taking regularly then 0.5-1 mg above your usual dose, but not more than 2 mg at one time. Try to contact prescribing doc, you can also discuss other meds for underlying anxiety so that Klonopin (clonazepam) is more effective in such acute situations.