The market for microgravity aircraft flights appears to be in flux, with one company grounded, at least temporarily, while another prepares to enter the field.

Earlier this month, Zero Gravity Corporation confirmed that its G-Force One aircraft (a modified Boeing 727) is grounded. The engines, which Zero G Corporation leases from Amerijet International, have been repossessed. Amerijet has terminated its maintenance agreement with Zero G and is suing the company for $127,435.66. The amount covers maintenance fees which Zero G allegedly owes Amerijet.

To put that amount into perspective, Zero G charges $165,000 for a dedicated charter flight with up to 36 participants.

According to company spokesman Michelle Peters, “Zero Gravity Corporation is currently in the process of restructuring flight operations management” and hopes to return to flight soon. The company promises to post a 2015 flight schedule on its website in the near future.

Zero G provides microgravity flights to NASA as well as private customers. The largest private customer for Zero G was the Northrop Grumman Foundation’s Weightless Flights of Discovery program, which purchased 48 flights for teachers over a period of five years. The end of that program was no doubt a serious setback for Zero G.

NASA’s educational microgravity programs also use G-Force One. Recently, there has been a rumor that those programs might be coming to an end after this year. If true, that would mean the loss of another major customer.

Zero G currently charges $4,950 for an individual ticket, which includes 12-15 microgravity parabolas. At one time, the company had plans to expand from a single aircraft to a small fleet, slashing ticket prices by more than 50%. However, the microgravity market never developed as Zero G expected. (The unexpected financial recession may have been one factor.)

Meanwhile, Swiss Space Systems continues to move forward with its plans to enter the microgravity aircraft market. The company expects to begin offering microgravity flights in January 2015. Swiss Space Systems has announced flights at 24 locations around the world in 2015, with prices starting at 2,000 Euros ($2,590 at current exchange rates). The modified Airbus aircraft also offers premium and VIP sections, which will be available at higher rates.

One problem for Zero Gravity Corporation has been complaints from researchers. NASA has offered research flights on G Force One through the Flight Opportunities Program, but some researchers complained that the quality of microgravity achieved on the Zero G flights did not match that achieved on earlier flights flown by NASA pilots. This is believed to be due to differences in pilot training. The Airbus aircraft is more automated and will fly parabolas under computer control which should, in theory, eliminate those differences.

(It should be noted, however, that even the best aircraft parabolas do not achieve true microgravity. The best parabolas typically achieve levels of about 0.01g, which is technically centigravity.)

Zero Gravity Corporation is a subsidiary of the space-travel firm Space Adventures, which could decide to put more money into the aircraft operation. Space Adventures has shown more interest in high-end trips, however. The company arranged Sarah Brightman’s upcoming trip to the International Space Station on a Soyuz rocket and is currently working with Russian space companies to develop a circumlunar mission for two unnamed customers.