Annual report pursuant to Section 13 and 15(d)

PROPERTY, PLANT AND EQUIPMENT

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PROPERTY, PLANT AND EQUIPMENT
 12 Months Ended
Dec. 31, 2018
Property, Plant and Equipment [Abstract]  
PROPERTY, PLANT AND EQUIPMENT
PROPERTY, PLANT AND EQUIPMENT
Property, plant and equipment, including both owned assets as well as assets subject to capital leases, consists of the following as of December 31, 2018 and 2017 (in millions):
 
2018
 
2017
Vehicles
$
9,820

 
$
9,365

Aircraft
17,499

 
16,248

Land
2,000

 
1,582

Buildings
4,808

 
4,035

Building and leasehold improvements
4,323

 
3,934

Plant equipment
11,833

 
9,387

Technology equipment
2,093

 
1,907

Equipment under operating leases
—

 
29

Construction-in-progress
2,112

 
2,239

 
54,488

 
48,726

Less: Accumulated depreciation and amortization
(27,912
)
 
(26,608
)
 
$
26,576

 
$
22,118



As part of our ongoing investment in transformation, in 2018 we made prospective revisions to our estimates of useful lives for building improvements, vehicles and plant equipment which in general had the effect of lengthening the useful lives of these categories. This resulted in a decrease in depreciation expense and an increase in operating income of $286 million and an increase to net income of $228 million or $0.26 per share on a basic and diluted basis. Separately, capital investments in additional property, plant and equipment, net of disposals and fully-depreciated assets, resulted in an increase in depreciation expense of $257 million and a decrease to net income of $205 million or $0.24 per share on a basic and diluted basis in 2018. Combining both impacts resulted in a net decrease of $29 million to depreciation expense, and an increase to net income of $23 million or $0.03 per share on both a basic and diluted basis in 2018.
We continually monitor our aircraft fleet utilization in light of current and projected volume levels, aircraft fuel prices and other factors. Additionally, we monitor our other property, plant and equipment categories for any indicators that the carrying value of the assets may not be recoverable. No impairment charges on property, plant and equipment were recorded in 2018, 2017 or 2016.