Claiming that long-haul by LCC's has not been profitable doesn't mean it will be that way forever. The only "true" example of a significant LCC long haul operation in the last few years has been DY. Other so called LCC's are subsidiaries of legacy groups such as Level and Joon. All of these have been flying widebodies, with the likes of TP, EI and TS starting to fly narrowbodies across the pond we'll see how TATL air traffic take shape in the next few years.
Time will tell what F9 will do with 18 XLR's, I frankly doubt they will only be used for transcon and Hawaii
764, 789, 732,733,735,737,738,739,
752, 722, 717,74M,DC10,DC9,M82,
M83, M87, M88,310,319,320,321,332,
333, 343, 346,359,388,L1011,CR2,
CR7, CR9,CRK, E175,E190,ATR42,