I think other players have reported similar problem in Croydon server. In tempelhof, a lot of planes are not listed in aircraft markets although they are shown available for auction in their respective manufacturer page.
Not all aircraft that are on the list, are at the same time on the market. The aircraft will be set gradually on the market.
Okay, so then there has been a change in the system since yesterday? (Yesterday it was definitively different and there were more aircrafts on sale.)
IF this really is a change, please keep the following in mind (example from Stapleton):
There are 12 DC8-73AF publicly available, no plane is on the market (yesterday all twelve were available). As one of my subs uses these planes it’s quite disturbing that I now have to "hope" that the system will put just any of these planes on the market. As this plane isn’t produced anymore, it’s impossible to plan expanding - e.g. a DH8-400 can always alternativly be ordered at the factory. So if there isn’t any plane on the market for X weeks, one could be forced to more or less completly change it’s strategy. If this is intented I’ll have to accept that, but I can’t imagine it is…?
I think the system should make sure that at least a small number of planes (at least 1) is available if they can’t be ordered as new. I don’t care if 50, 30, 12 or 8 MD-82 (of 172 total) are available on the market, but "none" would be bullshit. If there is only a total of 12 as in this example it may be much more unlikely to get one.
This change might also affect the diversification of fleets that luckily took place after the start of the new market. So why change this again?
Finally: If this mechanism has really been changed, please leave us a note in the announcements as this is a quite important change for some players! (and please give some more explanations) (Thanks)
EDIT: Something I just forgot: Would be nice if the number of planes on auction would be corrected. At the moment it shows the number of planes publicly available (or "50" if the number is bigger than 50), but this isn’t the number of planes on the market… would make checking for new offers quite easier.
Someone has put in a code change and it hasn’t worked.
We kindly ask you for patience as we are busy in preparations for the 10th aniversary meeting next weekend. We hope to get it fixed before, but I can’t promise right now.
Thanks for the info.
[Clicked on the wrong reply button] 
I think the problem was not solved yet.
This seems to be a bug, not by design. For example on Stapleton, if you look in the manufacturers list today it says that 41 Airbus A300-600R are on auction, but when you click on the Market there are zero.
I agree with what has been said.
I liked the fact that ac that were not competitive with fixed prices became usable since their value dropped. Mean’t the game became more realistic compared to the dash8, 737-7/900 fleets that dominated the servers
Hopefully, the team will be able to fix this problem soon as it is really limiting growth(can’t grow any further as the aircraft are very expensive/not availible at the moment). But well, when the aircraft market is working again in a normal way I will have much money to spend 
I know that the team is doing it’s best, so I’m convinced that it won’t take to long.
Idd i hope they solve this problem. i can’t lease any plain. only for a higher price!
It’s really a big problem. I need some 333 but now there is only 1 in the market…
@lirtc: ha, same with me, also looking for any cheap A332/333/342/343 on fornebu, but only very expensive planes available…
On Croydon the aircraft seem to be coming back but not at the numbers I was expecting