Semi-private airline JSX (formerly known as JetSuite X), already a JetBlue frequent flyer partner, has inked a new partnership with United’s MileagePlus. Mileage-earning is distance-based, and there’s a promotion this summer that allows United’s members to earn up to 11 times the usual mileage flying on the airline.

Flying JSX means leaving from private terminals to avoid the crowds, and enjoying just 30 seats on an Embraer regional jet. Their route network centers around California, with some growth in Texas, Colorado and Florida.

Mileage-earning:

• 100% of miles flown: fare classes Y, B, E, M, V, S, D, and T
  
• 75% of miles flown: fare classes W, G, and Q
  
• 50% of miles flown: fare classes N, H, and P

For travel through August 31 JSX says that “MileagePlus members will also earn bonus miles to help you get to your next award even faster.” I flag this also earn bonus miles, because it’s not exactly clear from their presentation whether the following table represents total mileage earning or the bonus.

• General members: 5x miles
  
• United Silver: 7x miles
  
• United Gold: 8x miles
  
• United Platinum: 9x miles
  
• United 1K: 11x miles

This bonus structure matches United’s revenue-based earning formula, and I presume it’s inclusive, but it might be more generous based on JSX’s wording (6x/8x/9x/10x/12x).

How does this cash out? Take the roughly 1100 mile Westchester – Miami route. If the 11x multiplier for 1Ks just means 11 times the miles and not an 11x bonus which would be even higher – top tier United elites earn 12,000 miles one-way on this medium-distance domestic route during the promotion period provided tickets aren’t booked in the lowest fare classes.

Unfortunately this very generous bonus “may be earned for a maximum of one time and is not combinable with other offers.” Update – JSX however says their terms are wrong and the bonus can be earned multiple times.

JSX and United are planning “more cooperation” to be announced later this year.