You might want to check with an engineer regarding the safety of a cracked dash cover as it relates to airbag deployment. I don't see how it could have any effect. The air bag deployment is triggered by sensors, not the condition of the dash covering it.
Actually, the issue on the FX models was not a crack issue but a defective part issue. It seems a significant number FX dashes had a 'bubbling' problem that made the dash appear it was taken out of a fry pan as you can see in the pic below.
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Infiniti did not immediately agree to replace the dashes, but after losing class action suits in states like Missouri, they issued the following letter to owners: It was not an actual recall, but an extension of warranty coverage that limits the number of owners who will qualify.
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Our problem is cracking which is a completely different issue which is caused by age, weather and temps, and even improper care or after market dash dressing applied by owners. Should the dash on a 50-70 thousand dollar car have a cracked dash in less than 15 years of use? Absolutely NOT. But no car maker is going to pay to replace thousands of dash covers for cracking. This is not a safety issue or defect issue. It's probably due to using a less than highest quality part. Replacing the cover is VERY expensive and some here have installed their own dash cover on top of the exiting dash. You can find DIY's in the FAQ section. In the area of the passenger airbag, I scored the underside of the new cover to allow (I hope) the bag to deploy if needed. I may eventually re-do that area to include a 'flap' that is held in place by velcro over the air bag area similar to the pre-made dash covers like "DashMat".