Unless you have a real compelling reason to go with such a wide-ranging lens, I’d question the wisdom of acquiring one.

Admittedly my 28-300 spends most of its life on my film SLR these days (a function it performs very well). Andy’s advice is good and it’s something I didn’t really think of, there actually isn’t really much point in getting something that covers most of the range you already have but with less quality unless you plan on using it to shoot other things (i.e. non-aviation photography which is what I generally use my 28-300 for). As Andy suggests, maybe try looking at a decent dedicated wide angle lens instead? The quality will certainly be better.

Paul