The strength of a knot is by design, some are stronger than others. Security of a knot is determined by the way the end of the rope is finished or locked in the knot. Secure knots as necessary and not as secure as possible. The US FAA has published AC 20-35C Tie-down Sense, with tips on aircraft tie-downs.
Below you will find part one, for part two click here.
Part one, pages 1 - 10, presents tips for general use to aircraft tie-down techniques and procedures. Its from 1983, dated but still actual.
Excerpt from the document:
Purpose: This advisory circular provides updated information of general use for aircraft tie-down techniques and procedures.
Cancellation: AC-20-35B, TIE-DOWN SENSE, dated April 19, 1971, is canceled
Background: Each year numerous aircraft are needlessly damaged by windstorms because of inattention to weather forecasts, negligence, or improper tied-own procedures. Windstorms may be broadly classified as cyclonic storms or low pressure systems, regional or localized terrain induced winds, thunderstorms.
To continue reading see the pdf below: