It means (1)high up in the air（高架在空中） .那座桥凌空架在两山之间that bridge spans between two hills。 (2)across the sky（从天空通过）.飞机凌空而过 ——the plane is flying across the sky.（3）rise high into the air（高升到天空,耸立空中）。悬崖上有座凌空高阁。there is a towering pavilion on the precipice .(4)凌空射门（volley shoot）也很常见，因为射门时球就是在半空中的。 ps:"电梯有临空"貌似不对啊，可以说“电梯凌空坠落”‘电梯凌空’，“有”可能是受英语“there be /have=有”的影响，汉语中‘有’是个verb，一般+noun（名词）such as有时间，有问题...也可能受方言影响，just like “yiyiitalophile”said，“this structure of grammar is more like chinese(taiwan、fujian) and cantonese”

it means it is available.

"临空" literally means above air; but I don't think it's appropriate to use it here--since it would mean "The elevator has risen above air, so you won't be able to catch it."

估计是电梯坏了，卡在半空中了。 应该是凌空，不是临空

To use “有' as Link Verb, this structure of grammar is more like chinese(taiwan) and cantonese.