When Virgin Atlantic's Little Red service launched this past March, it was the British airline's first foray into domestic flights within the U.K.. The all-economy service offers flights between London's Heathrow and Gatwick airports and Manchester, Edinburgh, and Aberdeen. The flights are timed so they provide easy connections for people transferring to and from Virgin Atlantic's long-haul flights, and offer free luggage and in-flight snacks (and breakfast on flights before 9 a.m.).

However, it has just been reported that Little Red's flights are running at one-third capacity, prompting one reporter to brand the new venture "financially disastrous."

We wondered why this might be happening, and whether there were better, cheaper options for domestic travel in the U.K.. We tested the rates using an October 28 travel date as a baseline. The lowest available fare for a Little Red one-way flight from London (Heathrow) to Edinburgh on that day is £70.30 ($112.47). Here's how that compares to other options for transport between the two capitals on the same day.

Compared to other airlines:

Easyjet (from Gatwick): The lowest available fare is £56.99 ($91.18) for an 8:55 p.m. flight. However, you'll have to add on an extra £1.42 ($2.27) if you want to pay with a credit card (no charge for debit cards) and a hefty £11 ($17.60) per bag.

Flybe (from Gatwick): £138.98 ($222.35) if you are only flying with hand luggage; £192.98 ($308.75) for baggage weighing up to 20kg (44 lbs).

The major carriers: Interestingly enough, we found the lowest available rate on a non-budget airline: British Airways is offering fares to Edinburgh for as low as £39 ($62.40) (with only carry-on luggage) or £49 ($78.40) (with up to 23kg -- 50.7 lbs -- of baggage) from London Gatwick. British Airways, of course, offers complimentary drinks and snacks, and the flight time is only 1 hour and 25 minutes.

Compared to the train:

Trains offer the benefit of truly local travel. If you're not headed for a main city, you can likely get closer to your destination than if you fly. On the other hand, it takes longer, and if you are transferring from a flight, you'll need to get to a central London train station from the airport.

Our experience used to be that, unless we booked months in advance, the train would be more expensive than flying. However, on October 28th Virgin Trains from London Kings Cross Station to Edinburgh Waverly Station, the lowest available fare is £63 ($100.79). This journey takes 4 hours 22 minutes.

Compared to the bus:

Sure, you could take the bus. It's certainly certainly cheap, but, unless it's your last resort, we'd only recommend the 9-hour-and-35-minute journey for masochists. National Express has a £15 ($24) fare available, leaving London Victoria at 9 a.m. and arriving in Edinburgh at 6: 35 p.m..

Conclusion:

Much to our surprise, we found the cheapest way of getting from London to Edinburgh was with a legacy carrier (British Airways). The Little Red service, which flies out of Heathrow Terminal 1 and is scheduled to meet long-haul flights, is probably only the best choice if you are connecting from another Virgin flight; or from a different airline flying into Heathrow.

Overall, it's an interesting lesson: You shouldn't always rely on a "budget" airline to give you the best fare.