This would kill an unknown amount of your passengers, likely the elderly and very young. The typical terrorist, if we even have enough data on them to say such a thing, is an adult male in good physical form. They have the strength and endurance to provide a threat at they very least, not something a sizable percentage of the other passenger may have. The passengers that do survive such a sudden exposure to hypoxia would be at a very increased risk of long term health and mental issues. This is very dependent on the time in hypoxia.

Your father thinks that blacking-out is similar to the movies, in that there are fast acting tranqs and other things that will 'knock out' a person and then they wake up with a headache. Anesthesiologists take at a minimum about 12 years of training before they touch a patient, even for 'low risk' dental procedures. Trying to black out a plane full of highly agitated people until the pilots can land or 'do something' about terrorists in the act is a total fantasy and may cause more deaths from false alarms and faulty wiring than the terrorists would have caused.

[0]https://en.wikipedia.org/wiki/Choking_game [1]https://en.wikipedia.org/wiki/Cerebral_hypoxia