Phantom traveler is the fourth episode of the series and as such, there are a lot of things that haven't happened yet. More importantly, there is a lot of information that the brothers Winchester haven't learned yet. Their dad's journal, while full of extremely useful and lifesaving information isn't an infallible source. There are multiple examples throughout the series where inaccuracy and scarce info put the boys in danger. So later, the boys learn better ways to exorcise demons from both Bobby and their father as well as the secrets of the Solomon trap. Additionally, the exorcism used was a two part exorcism in the episode, the first part released the demon from the body, the second part was the send back to the pit. Thus the scrambling for journal as the demon made on last attempt to send the plane into the dirt.
The reason that the christos thing didn't continue, and this part is speculation based on the later events and the personalities involved, is that it alerts the demon without putting it at a tactical disadvantage. If you had a choice between tossing some holy water to put a demon on the ground or saying the name of God and alerting the demon you are on to them, I would think the smart money would be on the ground.