I'm still considering my itinerary options -- if I do this it will not be in pure mileage run style, but will include some leisure travel, which requires other calendar considerations. Since I don't see it noted above, I wanted to mention/remind that in addition to a JetBlue credit card, the Paisly booking portal can be used to pick up extra points and tiles along the way, particularly if one is planning overnight hotel stays: https://www.paisly.com/. (For myself, I am about 1/3 of the way toward Mosaic 2 for the year, and would aim to front load costs/tile earning for this challenge in order to get to easier access to extra legroom earlier in the process).