UPS Inc. lowered guidance on its second-quarter earnings by about 15%, less than one week after FedEx Corp. posted its first quarterly loss since 1997, demonstrating that even the two largest corporations in North American freight transportation, with the most far-reaching global footprints, are ultimately not immune to the continuing struggles of the all-but-stagnant U.S economy.

YRC Worldwide late Tuesday reaffirmed its core second-quarter earnings guidance, but said its financial statement would include some special charges.

Canada-based transportation firm Trimac Income Fund said its first-quarter net earnings fell to C$600,000, or about 2 cents per unit, from C$1.5 million, or 5 cents, a year ago.

FedEx Corp. said late Friday it is cutting its fiscal fourth-quarter earnings guidance, blaming a steep increase in fuel costs.

Volvo AB’s earnings rose 12% to about $707 million, as sales in Eastern Europe Russia offset North American declines, Bloomberg reported Friday.

Wireless-services provider Qualcomm Inc. said its fiscal second-quarter earnings rose 5% to $766 million, or 47 cents a share, from $726 million, or 43 cents, a year ago.

Truckload carrier Knight Transportation’s first-quarter profit fell to $11.4 million, or 13 cents a share, from $16.6 million, or 19 cents, a year ago.

Truckload carrier Celadon Group’s fiscal third-quarter net income fell to $149,000, or 1 cent per share, compared with $3.9 million, or 17 cents, a year ago.