Mankato (KMKO)-Performers for this weekend's Minnesota Air Spectacular will begin arriving in Mankato tomorrow.  As many 40,000 people expected to attend, so safety is the first concern for those in charge.  Sound from a jet engine can reach 160 decibels, compared to 65 decibels for a normal human conversation.  Mayo Health System is donating 5,000 pairs of disposable ear plugs to the Mankato and Key City Sertoma Clubs for use during the show.  The other safety concerns are sunburn and staying hydrated.  You are advised to use sunscreen and drink plenty of water, because coolers will not be allowed at the show.