The following objects are masked by ‘.GlobalEnv’ and not appeared correct data

When I installed package 'hflights', the following warning message came:
package 'markovchain' was built under R version 3.6.3.

I do not know why above message came but I have installed the package markovchain some months ago.

library(hflights)
The package will be added: 'hflights'
The following objects are masked by ‘.GlobalEnv’

hflights

str(hflight)

The followings in hflights are correct
UniqueCarrier : chr "AA" "AA" "AA" "AA" ... But mine is UniqueCarrier : chr "N/A" "N/A" "N/A" "N/A" ...

Please advise how to fix to show correct dataset.