To interline or not to interline, that's the question

So guys, what do you think. What's your strategy/opinion?

Is it better to interline, why?

Or is it better not to interline, why?

I tend not to interline. 

I think without interlines you understand better how your airline is performing - your strengths, but also your weaknesses, which help you to fix them. You grow organically... and if you are big in an airport, usually your competitors will stay away unless there's an interline.

Imagine there are two airports with good demand. A to B. You, based on A, already operate 6 daily flights. The competitor, based in B, starts one daily flight to A, and request interline. I think you are better off without interlining, because with the interline you are helping him to fill that daily flight - without the IL it is likely that he will not fill with good loads that flight,... he won't launch a second daily flight, and in the future, he even might drop the flight completely, living you alone on that route. 

I have completely opposite view, because interline allow you to do math 2+2=8

In simple words, if both partners have equal ratings, both are better off with interline.

I usually say yes! I have always believed in interlining with competition so that can't stop me. What can stop me is cost. If I fly a few flights to a place and the IL costs over 100k its way cheaper just dropping the flight. Though you never want to make enemies so just send a nice letter saying why you cant interline at the moment but you are of course open to future collaboration. Others who I usually won't interline directly are with new airlines who I don't believe will make it. If the IL makes sense I will just wait a month or two and then sign it. Or depending on the size of a market and the personal relation to a partner I won't IL with his competition. If I have a good friend in the EU I probably won't IL with his competition out of respect. Though if I don't know the people I would try to IL with everyone in a market. Alliances might also have exclusivity agreements which cant be broken!

One rule, never cancel an IL if not out of extreme desperation! For me, it was extremely rude when players canceled as I had to change schedules and slots were usually tight.

Usually interline brings more traffic for both parties. However, if you have no problem filling the plane, and would like to keep all slots at your hub airport to yourself, then not interline is a way to deter other players.

If the potential player is sharing a hub with you, then interline will certainly bring much more connection traffic. However, the question is that how long would such a relationship last before a fight starts for the limited resources. For domestic interline, it will only make sense when you can coordinate a mechanism to prevent that infight from happening. (forming a Syndicate to coordinate prices and capacity, for example. No one will prosecute you in airlinesim :) Actually, also in real life as long as there is some cover up ;) )

Case A: you want to play friendly. Then interline with others.

Case B: you want to dominate a market / country. Then don't interline with everybody.

Then there are quite many steps between these extreme situations as well. It depends on so many factors.

I wouldn't make it on the "play friendly" or "dominate" decission. I would suggest to have a good look at the interlining partner, if this one is gaining some benefits for your network or not (and vice versa of course).

I would like to accept/request interline when it's a win-win.

I tend to partner foreign airlines or airlines that can extend my network (without hurting my own connection). So if I'm focusing on domestic routes, then I would in general deny any domestic competitors but request/accept interlines from long-haul international operators. If I'm operating a long-haul route, any other player on this route is my "enemy" ;)

I notice quite a few interlining requests and check the schedule screen.  Many of them are outside of the connection window and place them on hold.  I really don't accept interlining requests as readily as I used to.  I try to play on my connection strengths however there are some operators out there that much like what EastAsiaAir said, creates a win-win.

Example A

My airline is based in GIG, I fly a daily 788 to LIS. It’s not quite full all the time, but it’s making profit. New airline starts in LIS, and wants to interline. I would be a fool to say no.

Example B

My airline is based in GIG, I have a large operation, and am considering expansion into GRU. A new airline starts up in GRU before I get a chance with a large number of old planes. Do I interline? This one would require a conversation with that person as to what plans they have. Creating a partnership might be a good idea for both of us.

It’s always tricky, but in general I prefer to interline.

It depends on whether it is beneficial for a specific market. For huge markets like USA, China and EU, it is always better to IL with an airline which offers flights throughout the day. For airlines with wave format, it is usually tricky to match the timings to their hub when you are offering a wave system of your own.

One more case is when a large airline is based in a 5 or 6 bar airport. It is better not to interline as  the connection you offer to this hub might not be able to recover the costs of interlining. Though it might work in a case when you can fill a larger plane like A321 or a widebody.