Why did Warren Buffett dump all of Berkshire Hathway's Airline stock and incur a 4-billion dollar loss?

I have a tenant that is an industrial asset manager for multi billion dollar REIT and she said their company has two types of managers, ones that are handy/tool type guys that are real hands on personality types and managers that are real good at the numbers and analyzing the financials,planning, etc.

Traditionally Monthly Residential Lodging for business travelers has been called - Corporate Housing - estimated at $10 billion in annual rentals in the US (according to the last SKIFT conference). 

As you now have to pay labor to yank up tack strips, and a billion staples.

Definitely puts a damper on the charitable billions a year, of taxpayer money, that's sent to other countries.

Even a six figure loss doesn't register a blimp with a bank that has billions or even trillions in assets.

No multi million or billion dollar real estate investor saved up and bought it all in cash.

I wouldn't have thought it was a big deal until I Googled trampoline statistics....guess they are quite dangerous.More than 1 million people went to emergency departments for trampoline-related injuries between 2002 and 2011, with nearly 300,000 of those injuries involving broken bones, according to a new study.And these injuries don’t come cheap — the Journal of Pediatric Orthopaedics studyshowed that the total emergency department expenses for them was $1 billion, and more than $400 million for fractures specifically.What you really care about is making sure that they are taking the risk so just create a lease addendum that gives them permission and makes them assume liability.  

He’s sat on both sides of the table on over $1.7 billion of real estate deals.

But it's different than if you were a multi billion dollar private equity fund.