This is the latest installment of my “best time to buy airline tickets” series, featuring profiles of major U.S. carriers. It began with Southwest, followed by AirTran, then American, Continental, and Delta. More profiles are in the pipeline; meanwhile, here is my latest effort: Frontier Airlines.

A Brief History of Frontier Airlines

The original Frontier traces its lineage to the old Monarch Airlines which was formed back in 1946; for the next 40 years, Frontier was known as “Denver’s hometown airline”. Ultimately, the financially troubled carrier was taken over, first by People Express and later by Continental.

In the 1990′s a “new” Frontier was formed by a group that included former executives of the “old” carrier; in 2009, Frontier was acquired by Republic Airways – along with Midwest Airlines – and the two airlines will continue under the Frontier name. Airline headquarters is in Indianapolis.

Frontier Hubs and Passenger Stats

According to Frontier, their hubs are located in Denver, Kansas City and Milwaukee — this can be a bit of a misnomer as Denver has around 170 daily departures and the others less than ten. Frontier has alliances (code share agreements) with Midwest, Chautauqua and Great Lakes Aviation that extend its route system to service over 100 cities.

The airline has more than 50 Airbus aircraft, all with seat-back video screens; its 30+ Embraer planes will all be equipped with WiFi by the end of 2010.

Frontier’s Animals on Airplanes and Video

Frontier’s planes are easily identified by their unique “tail animals” (that’s Larry the Lynx and Jack the Rabbit in the upper right-hand photo); over the years, many of the animals have starred in well received TV commercials for Frontier, including the one below.

Frontier Sales and Deals

Frontier does not have regular sales with the precision of, say, Southwest and its Click ‘N Save deals, but when Frontier does have a sale, it’s often a good one. Recent sales included fare specials complete with free checked-bags, and another featuring one-way flights as low as $29 (not including taxes and fees).

Also, when other airlines launch sales (which you can see on our airfare sales and airline deals blog), Frontier is quick to match prices on overlapping routes.

As you can see in the chart below, the average cheapest roundtrip airline ticket departing from Denver to the top 50 U.S. cities is very competitive; prices have been rising over last year and it remains pretty volatile (meaning that changes occur frequently):

Keep up to date with our airfare deals blog with an RSS reader or follow on on Twitter (@farecomparedeal).

When to Fly on Frontier

On most airlines the cheapest day to fly is Wednesday; other cheap days to fly are Tuesday and Saturday, and many Frontier sales are restricted to these days.

Taking a deeper look into Frontiers flight schedules shows that, oddly enough, Wednesdays have more seats than other days of the week – still making it the cheapest day to fly, but this is outside of the normal airline pattern of maximum seats on Monday and Friday. This is probably due to the difference in Frontier’s mix of passengers compared to other airlines.

That’s why it’s a good idea to always consult a “flexible airfare calendar search” (you can see one right on our homepage) – a flexible calendar makes shopping so much easier, since it lets you see the cheapest dates to fly instantly.

Buy Frontier Tickets Early in the Week

For months now, Tuesday at 3pm Eastern has been the best time to buy airline tickets, no matter what the carrier. This is because an airline generally begins a sale late Monday evening, which prompts the other airlines (such as Frontier) to jump in the following day, with matching prices.

However, recently Frontier has been jump-starting its sales by launching them early Monday (filing fares late Sunday), and it remains to be seen if this trend will continue – again, keep up by following an airline airfare deals blog.

Remember, “Sale” Seats Go Quickly

If you see a great deal, don’t delay – great deals do not last long. On average, only about 10% (or less) of an airplane’s seats are ever “on sale”. Those who delay don’t get the cheapest tickets.

The 411 on Frontier Deals

As a “low cost carrier”, Frontier airfare is often available with as little as a week’s advance purchase and sometimes less. However, Frontier sales sometimes require a 14 day advance purchase, so again – it would be wise to check with a “flexible search calendar“.

Follow Frontier on Twitter, Facebook

Frontier is always busy on its Facebook page, and is a very helpful presence on Twitter (@flyFrontier) with 3,400 followers. Look for deals in both places, but even more important is the assistance you can receive when there are problems with flights.

In fact, Frontier’s Twitter communications are studded with responses from its PR team like, “How can I help?” and “Can you DM me your reservation code and details?” They pay attention and they try to make things right (and we can show you how to follow Frontier or any other airline – it’s easy).

Get the Best Prices with Frontier Every Time You Shop

For Frontier and other airlines, follow these simple steps: sign up for real-time email airfare alerts – follow the airfare deals – shop Tuesdays at 3pm – and get yourself involved in social media. Do these things and you will save.