In this task, you are given a context tweet and an answer. Your job is to generate a question for the given answer based on the given tweet paragraph. Note that your question should be answerable based on the given tweet, and the answer to your question should be the given answer.

Context: Tough day to fly to, from or through DFW. 30% of flights have been canceled already. Fog then to Ice. chad myers (@chadmyerscnn) March 4, 2015 Answer: 30 percent.
what percentage of flights is canceled?