The first is the appearance of a new airline at LAX. Allegiant Air started service from LAX on the first of the month. Unlike Virgin America and Jet Blue (expected next month), Allegiant is not going head-to-head with other carriers at LAX. In fact, most of Allegiant's destinations will be new offerings; only Monterey, California, and Medford, Oregon, already receive service from LAX (Monterey: United, via Skywest; Medford: Alaska, via Horizon). New destinations will include Bellingham, Washington; Missoula and Billings, Montana (the only service to Montana); Fargo, North Dakota (also the only service to that state), and McAllen, Texas (whose previous service from LAX ceased when the Delta Connection - Jetlink operation ended last year). Wichita, another city formerly served by Delta Connection - Jetlink, will also regain service (again, the only service to the state of Kansas). Other new destinations will be Des Moines, Iowa, and Sioux Falls, South Dakota (yet more previously unserved states). I think Grand Junction, Colorado, is also on the list. So far, Allegiant's operations here are pretty low-key, using only one gate and a couple of flights each day.
Allegiant's appearance doubles the number of MD-80 users at LAX: American is our other MD-80 operator, and in a big way. Alaska previously used MD-80's here, but they were retired last year; Alaska's operations here are now all various 737 models.
Some other carriers have added some new destinations: AirTran, which already operates several daily flights to their Atlanta, has expanded to Baltimore - Washington and Milwaukee. Both of these destinations were dropped at the end of last summer. Also dropped at the end of last summer was Spirit's nightly flight from/to Fort Lauderdale, which has just resumed. Meanwhile Canadian carrier WestJet has supplemented their Calgary service with a new flight to Edmonton, using a B737-700. Previously Edmonton was only served by Air Canada via their Jazz regional partner, in a CRJ-900. WestJet has also started using larger B737-800's on the Calgary route. Unlike the others just mentioned, the WestJet service to Edmonton is really new, not just a resumption of previously suspended service.
AeroMexico has also started bringing in B737-800's. Unlike their older aircraft, these have all-over paint schemes. I have seen a few B737-700's in this all-over scheme as well.
Summer is not the only time we have 'seasonal' flights; earlier this year we saw now-suspended service to a number of winter ski destinations: Montrose, Aspen and Eagle, Colorado; Jackson Hole, Wyoming; and Mammoth, California. Sometimes we get extra flights to the Mexico tourist places during the spring break season that will continue on into the summer, namely Cancun, Puerto Vallarta, and San Jose del Cabo. Similarly, Los Angeles is considered a seasonal destination by several foreign carriers, so far none of which I've seen return: Aer Lingus, LTU, and Air India.
LA Times: Allegiant Air's prudent ways help it soar amid slump in travel