Morgan Stanley believes now is an opportune time to buy shares of Frontier . “With the SAVE merger pursuit now in the rear-view mirror, we view Frontier as the quintessential ULCC (ultra low cost carrier) due to its ultra-low fares, ultra-low cost structure, and attractive (normalized) margins,” wrote analyst Ravi Shanker in a note to clients Wednesday. Shanker resumed coverage of the budget airline with an overweight rating, noting that low-cost carriers across the board should continue to benefit from pent-up demand for travel and easing fuel costs. At Frontier in particular, Shanker believes shares are trading at attractive levels as he expects the company to generate strong non-ticket revenues and notch a fresh ancillary revenue per passenger record boosted in part by capacity growth and higher available seat miles. According to Shanker, “ULCC valuations more than reflect the near-term capacity constraints, while giving the space little credit for an extremely strong topline and (relatively) easing jet fuel inflation pressure, setting up very attractive risk-reward.” Shares of Frontier have slid more than 6% this year and 12% since the start of August but could rally 57% from Tuesday’s close based on the bank’s $20 price target. — CNBC’s Michael Bloom contributed reporting