Following on from this (can-you-use-a-spelljammer-ship-to-get-to-ravenloft) question, I seem to remember that Krynn is similarly impossible to get to, mainly for plot reasons since no character on Krynn can get higher than level 18.
Anyone any thoughts on this?
Apparently there was an entire book on the topic of Krynnspace. There's since been a fan book updating that material. The Dragonlance FAQ confirms the connection. So Krynn looks pretty accessible, assuming you want that in your game.
Adding to Bryant's thorough answer, I would add the series of Spelljammer novels, the Cloakmaster cycle, starts with a Spelljamming ship crashing on Krynn.
The bit about high level characters being forbidden by the gods of Krynn is mentioned in the Dragonlance sourcebook for 2nd ed, but unless your party is already above 18th level I don't see how that would interfere with Spelljamming fun in Kyrnnsapce.
The answer depends on which time period your game is. While there are a lot of early materials describing Krynnspace and travel between that crystal sphere and many others was detailed, later AD&D 2e material differed. In particular, after the publication of the novel Dragons of Summer Flame in 1995, Dragonlance setting enters the Fifth Age, the Age of Mortals. TSR's default line of DL products starts to use the SAGA system; while the published modules keep on supporting AD&D.
As a concrete example, consider the AD&D 2e sourcebook A Guide to the Ethereal Plane (TSR 2633) published in 1998. It clearly states that access the Krynn is blocked against ethereal travel:
Chant is that this world fell under the sway of some chaotic power. No one knows if that's the dark of it, but fact is, a body can't reach Krynn any longer. Many bloods've tried, but they all return rattling their bone-boxes about ether gaps and creatures born out of chaos. If that's the truth, then the Border area around Krynn's been blocked.
Phlogiston's relationship with the border ethereal is not very clear to me, but I believe the block would also apply to spelljamming as well.
I think that post-Dragons of the Summer Flame there was some sort of shakeup regarding Krynn's place in the cosmology, preventing access to the crystal sphere by spelljamming vessels. However, I can't find a source for this claim. I thought it might have been in On Hallowed Ground, but I seem to have been mistaken.
It's as easy as you want it to be. It's your game.
On a more helpful note, I can only echo what others have said; as I recall, Krynnspace is one of the major locales in Spelljammer, so that would suggest that it's not difficult to reach.
In addition to the information laid out in the other answers, the gnomes of wildspace are descended from Tinker gnomes, who emigrated from Krynn, an have since spread to basically everywhere. Not only is it possible to get there, but there are native techniques to leave.
I cannot cite a source for you, but I recall this as well.
Golden rule is trump here: if you want to go, you can (even if no-one else can).
I remember that in DLS4 Wild Elves Dragonlance Module...
a crashed spelljammer ship commanded by drows appears in a hidden valley of the mountains in Southern Ergoth
So it's possible to use Spelljamming to arrive to Krynn (also I found references to Krynnspace a product published by TSR in 1993 with the reference SJR7
Agreed, there are only a handful of TSR approved sources of Spelljammer material out there and one of them is the cloakmaster series. Most of the first book of that series takes place in Krynnspace. Besides, they've got tinker gnomes... nuff said.
