Cardboard cycle box
Pros:
• Bikes have some level of protection from damage in transit.
• Everything is in a box with accessories like bottles, pumps etc. can be left on the bike.
• Boxes are free from cycle shops.

Cons:
• More likely to be stacked or mishandled which could incur damage.
• May need a replacement box for return journey.
• With front wheel removed, risk of damage to front chain ring and derailleur, unless protected especially.

CTC plastic bag
Pros:
• Baggage handlers can see it is a bike and are more likely to take more care.
• It is cheap at only <£10 a bag.
• Very little of the bike has to be dismantled.
• More likely to be placed straight on a trolley rather than being sent down a conveyor belt.

Cons:
• Greatest risk of damage if the bike is dropped or mishandled.
• Airline may not accept bikes in the CTC poly bags.

Soft Bike Bag
Pros:
• Bikes are protected from rubbing against other baggage in transit.
• Less risk of them being damaged.
• Everything is in the bag together; accessories like bottles, pumps etc. can be left on the bike. Also, with handles / compactness, easier to carry around.

Cons:
• Baggage handlers cannot see it is a bike and are less likely to take care of it.
• More likely to be sent down a conveyor belt which can cause damage.
• With front wheels removed, risk of damage to front chain ring and derailleur, unless protected especially.
• Initial cost of bag - expensive.
• Bike has to be dismantled to get it into the bag.

Hard Bike case
Pros:
• Virtually bomb proof protection for your bike in transit.
• Minimal risk of them being damaged.
• Everything in the case together; accessories like bottles, pumps etc. can be left on the bike.

Cons:
• High initial cost of a hard case.
• Hard cases are heavy and will eat into your baggage allowance.
• Bike has to be dismantled to get it into the case.

A couple of sites selling bags....
http://www.sjscycles.co.uk/category-Bike-Bags-and-Boxes-311.htm
http://www.evanscycles.com/categories/bicycle-accessories/bags
http://www.ctc.org.uk/DesktopDefault.aspx?TabID=5184

Removing Pedals:
Finally, whichever, option you have decided upon, these fundamental preparations are required for the flight::

• bicycle pedals to be removed (or fixed inwards) *
• handlebars must be fixed sideways
• the bicycle must be contained in a protective case or bag
• you may wish to deflate the tyres to reduce risk of damage
• Check bicycle package complies with maximum dimensions

*To remove the pedals:
         The left pedal comes off clockwise and goes on anti-clockwise.
         The right pedal comes off anti-clockwise and goes on clockwise.

Remember to add a pedal spanner to you packing list. If you do forget generally most pedals need a thin section 15mm spanner. You might want to try a practice removal before you leave home, as some bike shops tend to over tighten the pedals. A little bearing grease smeared onto the threads can help with easy removal.