Yes, it is true that our sense of smell can be somewhat duller on an airplane.
The lower air pressure and dry air inside an airplane cabin can impact our sense of smell and make it more difficult to detect certain scents. Additionally, the recycled air in an airplane cabin can contain a mix of various chemical and mechanical odours, which can temporarily dull our sense of smell.
Even studies have shown that the reduced air pressure inside an airplane cabin can impact our ability to detect certain scents, as the lower air pressure affects the way that scent molecules are dispersed and detected by our olfactory receptors.
This can make it more difficult to distinguish between different scents, and can also reduce our ability to detect the intensity of certain fragrances.
How good is your nose in the sky?