Code Sharing is when an airline uses flights run by other airlines to enhance customers abilities to book complete flights with them. For example, as British Airways has a code sharing agreement with American Airlines. This means someone booking a trip to New York on the British Airways website may, depending on the day of travel, be flying on a British Airways flight or an American Airlines flight.
Code sharing provides mutual benefits for both airlines as it means that they can offer more flights to people whilst minimising the number of empty seats. In addition, it also provides an opportunity for airlines to generate more traffic to their websites as a greater number of flight choices are available for customers. Furthermore, airlines can also offer flights to a greater number of destinations.

Customer Benefits
There are also a number of benefits for the customer. Firstly code sharing offers a greater choice of flight dates and times. In addition, customers can book flights to a greater number of destinations using the same website without having to make more than one booking. This also means that if flights are delayed for example, it would be easier to alter the flight plan by going through the website if necessary. When separate bookings are made this would not always be possible as one airline is not overseeing the whole flight path.
There is also an advantage when booking multi centre flights. For example, on the British Airways website it is possible to book a flight to from London to New York, an interconnecting flight from New York to Los Angeles and then a return flight from Los Angeles to London. This would not be possible without a code share between British Airways and American Airlines as the interconnecting flight would need to be run by American Airlines. Thus with the code sharing agreement, the British Airways website for example can effectively be used as a one stop shop for flights from the United Kingdom to the United States increasing convenience for customers.

Drawbacks to Customers
Whilst it does appear that there are benefits to the customer of code sharing agreements, there are certain concerns that have been raised online with regards to them. One comment flagged up suggested that organised flights are more costly. In addition, people have complained that when there are flight issues each airline in flight path blames the other one for the problem caused.
As one can see therefore there are some drawbacks to code sharing agreements for the customer. However, on the whole there do appear to be more benefits in terms of flight options as well as convenience. Airlines have ultimately moved into code sharing agreements with others in order to maximise seat usage of flights thereby reducing costs and therefore increasing profits. They therefore need to ensure that such agreements continue to provide benefits for customers and that complaints are minimised. We have to wait to see how this progresses.
However for the most part code sharing agreements are beneficial to customers. What are your views on code sharing agreements?