What mainly decides aircraft age?

If you must have noticed, some aircrafts fly for many years compared to others.
Aircraft technology has progressed in such a way that if aircrafts are maintained properly then they can technically fly forever, without having a need to replace them.
If experts are to be believed modern aircrafts can go on forever IF maintained properly and taken care off but there is an argument to this statement, I personally think this statement is only true to a certain limit but there are successful example of people using 67+ year old DC-3 aircrafts for cargo use even though this aircraft is a piston engine and is notorious for its thirst for oil.
Aircrafts life span is not measured in years but pressurisation cycle. This is specified by the manufacturer. Each time an aircraft is pressurized during flight, its fuselage and wings are stressed. Both are made of large, plate-like parts connected with fasteners and rivets, and over time, cracks develop around the fastener holes due to metal fatigue.
The life of an aircraft depends on the usage or even the range of flights it is put through. When a pressurised aircraft flies, it’s fuselage acts as lungs, compressing and expanding with the change in atmospheric pressure outside, so in my opinion aircrafts which are used over “short distances and frequent flights” have their mechanical life shortened if compared to aircrafts flown over “long distance not so frequent flights” because the compression and expansion suffered by the aircraft over “short, frequent flights” is much more and severe than encountered by “long distance not so frequent flights”.
When aircraft is on the ground ready to fly, the pressure inside the aircraft is a bit lower than the air pressure outside so the fuselage suffers compression (high pressure outside), as it flies at or above 10,000ft air pressure inside stays at around 6000-8000 ft (depends on the aircraft.), this pressure is higher than the pressure outside (since air pressure decreases with height.) here the fuselage suffers expansion.
So any regional jet will encounter more structural stress through its lifetime than say a Boeing 777 or a 747.
Daily scheduled flight say from LA to San Diego will encounter more stress flying up and down number of times if compared to a non-stop LA-London flight because the number of times a fuselage compresses and expands is drastically reduced when flying long distance at one decided altitude.
Why I am talking about all this is because during maintenance pretty much everything can be overhauled and replaced with new parts except the fuselage and wings itself, if someone decides to do it why not buy a complete new aircraft?


I would love more feedback on this topic since I am no technical ace neither am I an engineer.

Cheap is the way of the future for Airlines?

The current economic condition makes low cost airlines the necessity for present and future but economic condition keeps changing, people earn more money, splurge it and then they loose money and save it. Its a whole cycle which indirectly dictates the way an airline sells itself.
Why Low Cost Airlines?
The current economic condition shows how vulnerable airlines are, how much dependent they are on the market, Airlines are here to stay, they are a necessity for fast, cost effective travel. If airlines go cheap, more people will travel, more the profits.
In a country like India where the Airline tickets are one of the cheapest in the world, Airline industry has the biggest competition in terms of Indian Railways.
People like to travel cheap, specially for short distances, hence its not surprising that Low cost airlines are in profit where as three major airlines in India are in red.
Cutting cost is directly passed onto the customer, it also increases the profit a company can make.
There are many Low cost models but one of the most successful one is of South West Airlines, use one type of aircraft save the cost in maintainence, pilot/crew training etc...etc
If airlines follow such models all over the world, they would go in red only because of a better competition, competition in short is good for travellers as well as the better competitor, since cheap tickets equal to more flyers.
Airlines can go cheap by
1. Using one type of aircraft
save on training and maintainence costs
2. Go no frills
flyers wouldnt mind paying for food, some dont even want food on shorter routes
3. Go cheap with crew accomodation:
instead of putting them up in a 5star/4star hotel what they can do is buy/rent private residences locally, which would reduce the cost of crew handling considerably.
4. Give more cash incentives to the crew instead of some benifits.
5. Use somewhat low hour pilots as First officers:
the amount of salary to be given is reduced, plus to get hours pilots wouldnt mind less pay initially.
6. Start their own agencies to make profits:
instead of outsourcing and paying huge amounts or percentage, start their own agencies which sell tickets or do their own ground handling etc...etc
7. Maintainence
doing maintainence the proper way will save loads of money, eg: keeping the aircraft exterior clean etc...etc
8. Pass on the benefits to flyers:
device ways which will attract flyers to your airline, eg: paying them some cash if they are carrying less baggage.
9. Direct flights & better fuel management:
more direct flights will save lots of money, for international carriers, flying direct twin engine ETOPS aircraft might cut costs, better fuel management like eg: refuelling more in countries where fuel is cheaper, will further add to the savings.

- Akshay