CHICAGO (CBS) — Boeing’s troubled 737 Max fleet might not be back in the air for several months, as the aircraft manufacturer and regulators continue the careful process of making sure the jets are safe, according to one travel expert.

The FAA and aviation authorities around the world grounded all 737 Max aircraft last month, because of two fatal crashes in five months.

Airlines have been scrambling to modify their schedules, and it seems no one is expecting the planes to be flying again anytime soon. Southwest Airlines and American Airlines announced this week they are preemptively canceling flights and modifying schedules involving 737 Max jets through at least mid-August.

CBS News travel editor Peter Greenberg said he’s willing to gamble the grounding of 737 Max planes will last well into next winter.

“The recertification process for this plane is going to take a long time, because nobody wants to mess this one up, and as a result, I wouldn’t be bit surprised if we’re talking first quarter of next year before these planes fly again,” he said.

Behind the scenes, carriers are assessing what Greenberg called the airline science of yield; a flight that was supposed to use a 737 Max could be nixed, or another trip could be canceled to use that plane for another flight originally booked on a 737 Max.

“You bet they’re scrambling, yeah, and they’re performing triage,” Greenberg said.

With parts of their fleets now grounded, airlines must calculate which upcoming flights make the most sense in economic terms of the average fare per passenger per mile.

“How much can an airline earn from that seat? And if your flight doesn’t have a very high yield, then they’re inclined with or without the 737 Max to take that plane and allocate it somewhere else where that seat earns more money per passenger. So it’s a little bit of a game right now,” Greenberg said. “You can’t pick in a vacuum. They might keep a flight on because they know that it connects to a very good revenue flight going from Chicago to London, but if it doesn’t connect and it doesn’t make a lot of revenue, it may not fly.”

Greenberg warned travelers not to play roulette with fall flights. Check the plane type for your flight, and expect fares to go up.

“For people who have no reservations at all right now, their airfares – just based on the laws of supply and demand – are inevitably going to go up,” he said.

Boeing CEO Dennis Muilenburg tweeted out a video this week proclaiming “steady progress” on the path to making the 737 Max airworthy again, but there has been no official estimate of when the planes will be allowed to fly again.