Yep, I got this too. I did take one flight during the challenge period, but not enough to get it. On a flight last week (2/1), I got the Mosaic treatment and was confused by it until I checked my account and saw the expiration on 12/18.
Which program did you match from?
I matched from American Platinum. I flew on several awards, one paid booking, and a couple of family pooling paid bookings during the challenge period, got the credit card in early 2018, spent about $3,000 on it and took two paid flights in January, 2018. I also signed up for their other Badges in January, 2018 and received 100 points for signing up for Badges and the "Eat your Cake and Fly Badge" (500 points). JetBlue seems to always have issues with their website, so I wouldn't count on the Mosaic status sticking, but who knows.
The status stayed until 1/31/18. If you booked before it is YMMV to get mosaic benefits if the flight is after. Its not surprising that on a flight flown one day after the expiration that you got the benefits
All true, but in my case (and apparently for brodes18 as well), the website currently shows our status as valid through
12/31/2018. Further, I booked a ticket
today for travel next month and the reservation shows the usual inclusions (bags and Even More Speed) due to my Mosaic Status.