That leads to question how PAX allocation works. Basically PAX are spread over all offered service equally. So many small planes have advantages over one big.
Second step of that process takes many more valuables into account, like fare, flight times and duration,RI/CI and some more to change that allocation for bonus and malus values.
So it may make sense to oversupply route seatwise to win the greatest part of them.
Sometimes good offers (mainly good fares) make more people fly than prognosed (10-20%).
Sometimes it is just keeping opponents from getting good revenues, if your business can easily cope with losses.
Sometimes people just canīt calculate.
To OP: I would have suggested to experiment a bit more with that game in Beginnerīs World. Jet Age is one of the hardest scenarios, because of low traffic numbers and saturated markets.Thatīs another reason for oversupply situation, very hard to find a good spot for a startup.Itīs going to be tough.