Is this sentence It is desirable that the airplane as light possible correct?

No, the sentence "It is desirable that the airplane as light possible" is not grammatically correct. Here's why and how to fix it:

Problems:

* Incomplete comparison: "As light possible" needs to be completed with a comparison. You're comparing the airplane's weight to something else.

* Missing verb: The sentence lacks a verb after "desirable."

Corrected Sentence:

Here are some ways to correct the sentence:

* "It is desirable that the airplane be as light as possible." This uses the subjunctive mood for a desirable outcome.

* "It is desirable for the airplane to be as light as possible." This uses the infinitive form.

* "It is desirable that the airplane be as light as it can be." This clarifies the comparison.

In summary: You need to complete the comparison and add a verb to make the sentence grammatically correct.