Selling aircraft not possible?

I have an old airplane I'd like to get rid of.. 

Is there any way of doing this?

It's my property (on credit loan), but when I try to sell it directly to my mother or sister company, it doesn't show up in the dropdown selection (it's empty).

When I put it into the market, I can see it, but a friend of mine can't.

Does it mean that there's no way to actually sell or otherwise get rid of an aircraft?

go to asset managment then click aircraft transfer and it will give you several options

If craft in credit, you should pay out credit first and then have an opportunity to transfer. Or you can sell it in open market, but have only the difference between the cos of aircraft and payed out sum )

Well, that's the problem. The open market doesn't seem to exist anymore?

No one can see my aircraft in the list, and I can also only see aircraft of the Aircraft Trade and Leasing Organisation in the market..?

You can't see your own listings on the aircraft market.  At the top, there's a special tab which lists the aircraft that you have available for sale and/or lease.  Other players on the same realm will see your aircraft on the same page as the ATLO listings.

WHen I try to sell one of my aircraft, It shows up as a cash purchase only. It doesn't give the option for other players to lease using Aircraft Trading Co. I know this because I emailed the airlines who have majority of this AC, and one of them PM'ed me back saying its only a purchase option and he can't buy it cash.

http://community.airlinesim.aero/topic/3476-ende-no-leasingfinancing-for-private-aircraft-offers-keine-leasing-finanzierungs-option-fuer-private-flugzeugangebote/

The explanation for why.

You can offer it for a private lease if you have more than 20 million in equity. (Line entry in the balance sheet)