Background: I write as a traveller and not a formal expert, but I have made 50+ flight "legs" on either international carriers or on local carriers within Asia in the last 4 or so years. I take many photos out of airline windows and make a point of reading the rules that each airline has established. I use both a DSLR and smaller point and shoot cameras - the latter mainly for their video capability. I am a professional electrical designer - which 'informs' my opinions on the relative merits of various airlines' policies in this area.
A summary answer to your question is:
No restrictions during flight proper:
Every airline that I have encountered allows in flight photos out of aeroplane windows without restriction during flight proper - usually from when the "fasten seatbelts" sign is turned off after takeoff and climb-out until the point that you are advised to fasten seatbelts, put your seat back vertical and stow your tray table, just prior to final descent.
During this entire period - sometimes in excess of 12 hours on longer international flights, no concern has ever been expressed over use of cameras for any out-of window photos of any sort.
No use of electronic cameras during takeoff & landing:
Most airlines forbid the use of cameras and any other electronic devices during takeoff and landing.
The no camera rule usually starts when the plane is about to begin to be moved from it's boarding position. After landing many continue the prohibition during taxiing until the seatbelt sign is extinguished but some few allow their use soon after touchdown.
Some few airlines have a more enlightened and broader policy which also makes sense in reality. eg QANTAS allow use of all still cameras and video cameras with non detachable batteries during all phases of the flight including takeoff and landing.
The actual use of a camera in an aircraft is governed by the regulations of the airline concerned. While no modern camera is probably going to be a danger to the navigation systems, the rules for when you can and can't use them vary by airline, with some having tighter requirements than others.
Q: Do the bans make sense?
A: Very largely, no.
The fact that QANTAS allow unlimited use of anything up to DSLR level and other than external-battery video cameras indicates that they agree with my professional opinion re relative dangers.
I am not sure why QANTAS disallow video cameras with external batteries - it may be due to size, possibility of spark on external contacts (unlikely), prospect of batteries being dropped during changing (unlikely) or ??? Most non purpose built cameras with video capability are not affected by this ban - including essentially all video capable DSLRs.
Modern aircraft electronic systems are designed to be as safe as possible against the sort of threats which they may reasonably encounter during flight. As passengers are quite likely to use cellphones in flight despite bans on use, the aircraft systems MUST be proof against such use. The focused beam from a high power RADAR system can inject signals well above what a cellphone can achieve. (In another lifetime when I worked for Telecom NZ, we had an experience where a US warship docked in our capital city and left its main RADAR system scanning. ALL the phones in the city "tinkled" every time the RADAR beam swept across the main telephone exchange :-).
The level of EMI generated by a camera under worst case conditions will be far lower than from eg a cellphone. (Assume no super in-camera WifI transmitters etc).
So the use of a camera during takeoff and landing is very very very unlikely to pose a hazard of any sort to any aircraft system. Electronic equipment that is allowed to remain operational may present more of a hazard than a camera does. While computers, pdas, "tablets", electronic games, cellphone and smart phones in flight mode and more are required to be turned off during takeoff and landing, items such as watches, pacemakers (fortunately) and miscellaneous items of portable non-display-equipped electronic equipment are exempt or overlooked.
However, "rules are rules" and, while QANTAS allow it, and common sense says it does no harm, getting most other airlines to agree to in-aircraft camera use is "problemantic" at best.
All the normal social 'rules' apply, plus anything laid down by the airline, plus whatever the cabin staff may decide to add if they are having a bad day.
I find that in most cases if I choose to I can end up with most of the cabin staff in the rear galley for a group photo at some stage during the flight. On one occasion I managed most of the cabin staff PlUS the airline's safety training manager, plus an offer of personal assistance with finding sightseeing destinations next time I visited their country.
Related photo: May not be great portraiture but makes a nice addition to the trip record. (Here's where I discovered that the new expanding lens hood did nasty things to the on-camera flash field :-) ).
I have had no problems from staff while taking in-cabin photos of passengers with their permission. Not something I do a vast amount - but often enough to note staff reaction.
On a very few occasions the staff have got grumpy about general in cabin photography (which I try hard to keep to a minimum for trip record or whole cabin pictorial shots only). and suggested I limit in cabin shots BUT I generally don't take more than a few impressions and usually from the back looking forward, if I am not taking personal photos with permission. (Rear of cabin looking forwards with lights off and many monitors on looks good).
(1) Fly QANTAS :-)
(2) Otherwise, what you choose to do is up to you - and exceeding limits may cause you to end up in court. I have seen numerous people using 'point and shoot' cameras during takeoff and landing without airline staff complaint. A film SLR could probably be used and would probably not be seen as an "electronic device" even though almost all would be. A DSLR without LCD enabled may or may not be seen by airline staff as "electronic". The most likely interference from such would probably be the rather large current spike that occurs at shutter operation. The motor drive on a film camera would be worse.
Apart from airline staff reaction you need to assess for yourself the morality of using a debice which the airline has banned on "safety" grounds - no matter how reasonable suhc concerns may or may not be.
More soon ...
My experiences in recent years have been limited to "Pacific Rim" / Asia and a limited number of airlines. However, I believe that they would apply to most reasonably major airlines in many countries.
2004-2012: NZ, Australia, Singapore, Malaysia, Indonesia, Hing Kong, China.
Air NZ, QANTAS, China Airlines (Taiwanese), All Chinese airlines, Air Asia, Royal Air Brunei)
2001-2003: NZ, US, Brtian, France, Thailand, Taiwan.
British Airways, QANTAS, Air NZ, Eva air.
Often poor :-(.
Mr Boeings fine double glazed plastic windows with inbuilt vapor layer and often the appearance of sanblasting on the outer surface do not usually lend themselves to fine photography. And My Airbuses are usually smaller and optically no better. But some worthwhile photos can sometimes be obtained if absolute quality is ignored - which can be hard :-(
Papua New Guinea
North Eastern China
Definitely not China !
Crossing Australia from NZ heading for Asia - somewhere in inland Queensland - probably at about 35,000 feet. Colours are sure to be wrong but no amount of playing gave anything convincingly better. Manifestly too much yellow - but less looked worse :-(. Australian scorched earth summers plus irrigation tend to get extreme brown and green combinations - but not this extreme (probably). Double optically poor windows do not help. (At this altitude anywhere in China essentially all ground detail would be lost or fully invisible.
Still beautiful - double windows and all. Somewhere between Brunei and Hong Kong.