Winter has been a busy leasing season for The Grossman Companies, Inc., in East Boston near Logan International Airport as Diamond Express Air Freight signed a lease for 9,514 square feet at 230 McClellan Highway (Rte. 1A). Making the announcement was Richard McKinnon, Director of Brokerage Services for The Grossman Companies and Exclusive Broker for the Landlord, 230-240 McClellan Highway LLC. He negotiated the lease between the Tenant and Landlord.  With this deal, McKinnon has consummated four air freight leases along McClellan Highway comprising a total of 35,461 square feet and bringing the five-building air freight park to 96% occupied.  Only office space remains on the second floor of the buildings at 230 McClellan and 370 McClellan, with 1,000 square feet and 2,299 square feet respectively. Last month, McKinnon leased 13,947 square feet of warehouse and office space at 370 McClellan Highway to freight shipping and delivery services firm Skema Courier, Inc. In 2013, he leased 7,488 square feet at 240 McClellan Highway in East Boston to global logistics firm CH Powell Company, and 4,512 square feet at 240 McClellan Highway to AB Logistics for its air freight / logistics business.