The tragedy of MH17 has highlighted that passengers may not be aware of the airline they are flying with when booking.
MH17 was what is called a code- share flight. KLM Royal Dutch airline put its flight number on a Malaysia Airlines plane - so MH17 was also KL4103.
Only savvy travellers would bother to check the fine detail of their flight and who is operating it, although the KLM website goes to great lengths to show what airlines passengers are flying with.
Some travel agents and airline websites are not so forthcoming.
Codesharing has been used for decades but it is far more widespread now as airlines try to increase the size of their network and appeal to frequent flyers.
The vexing problem for passengers is they may arrive at the airport with their trip planned and hotels bookings made to find they are flying on an airline they may not like or trust.
From Amsterdam to Perth, for instance, KLM offers a host of options but only a few on KLM aircraft.
The first offering is on KLM to Abu Dhabi, transferring to an Etihad Airways flight to Perth. Both flights carry KLM flight numbers.
The second option is the ill- fated KL4103 operated by Malaysia Airlines as MH17. At Kuala Lumpur, passengers transfer to KL4107 for the flight to Perth, again operated by Malaysia Airlines.
The third option is KLM to Hong Kong, transferring to Cathay Pacific to Perth, while the fourth is KLM to Kuala Lumpur and Malaysia Airlines to Perth.
The final two options involve KLM to Singapore or Bali, transferring to Jetstar flights to Perth.
Passengers may often start a flight on a 747 jumbo or A380 super jumbo but end up on a tiny plane.
Some of the consequences of this are passengers may not want to fly on a small aircraft for safety or comfort reasons, and carry-on baggage on an international flight sometimes will not fit on a commuter aircraft.