Two of your best Las Vegas photo opportunities come up immediately upon your arrival and immediately after your departure... while approaching and taking off from McCarran Airport (LAS). First I'll address the issue of the announcement that's made at least twice during every flight, telling passengers to turn off all portable electronic devices.
I found some discussions about that topic here and here. (Scroll down to the Dec 05, 2006 post at the second link, where the poster states Camera (Digital or Film) CAN be used in the plane, even when it's taking off and landing. Camera does not transmit data through RF.
I think that poster is correct, since I've shot photos during takeoffs and landings at least 30 separate times without being scolded by the flight attendants or causing the flight crew to announce "hey, who's using an electronic device back there?" As the Kennysia poster stated, the airlines are concerned about devices which emit a radio frequency (RF), which cameras do not do.
Commercial jets sure do have some dirty and scratched up windows though. Surprisingly, you can still get some fairly good shots (I've posted some at the bottom of this intel) although I've noticed that daylight shots seem a bit desaturated (lacking color) even with the use of a polarizing filter. Night shots are very difficult since they require a slow shutter speed (one tenth of a second is about the fastest you can get away with and still have a visible image) and the plane is usually bouncing around enough to make holding the camera steady impossible.
If you plan to shoot some pictures from the plane window, the most important thing is to be on the correct side of the plane. Your odds are obviously 50/50, although you can increase those odds if you can find someone or some online discussion where travelers discuss the view during flights from your home city to Las Vegas.
Or you can try asking the pilot or flight attendants. I don't think pilots receive their instructions for landing until they are close to the airport, but they will know if a certain approach is more frequent than another.
Also, you don't want to be sitting next to the wing or engine as those will obstruct your view.
I've found that the best view during the approach to McCarran is from the left side of the plane; and the best view during takeoff is from the right. This has been true about 75% of the time.
From where I live in the Pacific Northwest, flights to Las Vegas normally pass over Red Rock Canyon which is just west of Las Vegas; and a view of the entire Las Vegas Strip will be offered from the left side of the plane. McCarran's runways are very close to Las Vegas Blvd. near Mandalay Bay and the Welcome to Fabulous Las Vegas sign. So your view of the strip will most often be from the south looking north.
I did miss a spectacular view out of the right side of the plane once though. We were redirected to the north and approached the airport from the downtown Las Vegas area. As we descended, the plane was almost directly over Las Vegas Blvd. and the Stratosphere observation deck looked almost close enough to touch as we passed it; then the Stardust filled the window as I sadly looked out from the wrong side of the plane.
If you have ever watched the TV series "Las Vegas" (with James Caan) you know what kind of spectacular aerial views Las Vegas offers.
I recommend using a small pocket sized camera vs. an SLR for these type of shots; at least 6 megapixel resolution if you're using a digital camera; and shooting in RAW format vs. JPG. While an SLR or digital SLR should produce higher quality photos, they are also more difficult to handle in an aircraft that's moving at high speed. So you may end up with poorer quality photos that are blurred. For bright daytime shots, blurring is much less likely to be a problem, as you can use shutter speeds as fast as 1/400 of a second or faster.
The more zoom you use, the more blurring can be a problem. Zoom is almost useless at night in a bouncing plane but works well for daylight shots.
If your camera has a feature that lets you hold down the shutter release to shoot several photos in fast sequence, that's the ideal technique to use. Just make sure you have good focus on the scene first. Like when shooting from the Stratosphere indoor observation deck, your camera may try to focus on the glass instead of the target scene. Holding the camera lens up close to the window will reduce the chances of focusing on the window glass or plastic.
Daytime shots can be taken in AUTO mode; but for night shots you'll have to switch to M (manual) or S (shutter priority) mode and adjust your shutter speed to 1/4, 1/6, 1/8 or 1/10 second. Maybe 1/13 to 1/25, depending on how bright the lights are in your target scene. Night shots from a jet window are probably a photographer's biggest challenge, as you usually only have about 60 seconds worth of interesting scenery in front of you.
During the approach to McCarran, the plane is slowing down and gradually descending; so you have more photo opportunities than during takeoff when the plane is accelerating rapidly at a steep angle.
In any event, you'll feel a great feeling of accomplishment if you can obtain some high altitude shots of the strip that frame the entire length from Stratosphere to Mandalay Bay, without any blurring. As you can see below, it is possible!