The time was about 9-9:30a.M, it was a cool, clear, sunny march morning with magnificent blue skies and good long-distance visibility. i was sitting at my kitchen table on the computer in the relatively open dining room/kitchen area with the bright skies lighting up the room. i heard a low-flying jet aircraft likely an airliner entering or exiting the pattern at boston-logan international airport (about 40 miles to the north of my house), it seemed slightly louder and more high-pitched than most of the usual modern airliners with high-bypass turbofan engines or acoustic liners and more like the older low-bypass turbofan engines on aircraft such as the md-80 series (or historically the boeing 727), the aircraft sounded lower too than usual, noting the high-pitched sound i suspected that it may not have been an airliner but possibly a air force reserve c-5a galaxy of the 439th airlift wing at westover air force reserve base out on a training sortie, as the last of the older c-5a models (all based at westover as this report was written) is due for decommissioning the before the end of 2017 my interest was peaked and i jumped to the window to get a glimpse of the aircraft. i looked into the bright blue skies but realized the airplane i heard had already passed out of view over my house, instead my eyes caught sight of something else much higher. the object appeared to be a shiny silver or grey metallic color but i am unsure if this was its actual color or just the sunlight reflecting off of it, it had the color and glint of an airliner at cruising altitude but unlike an aircraft i could clearly not see any wings or tailplane/horizontal stabilizers on the object and it produced no contrail, it was an oval, oblate, or rounded cigar shape to it with no visible appendages. i rushed out to my front porch to continue watching the object, it continued a very constant and swift path towards the south or southwest at an altitude i could not accurately determine but would guess to be in the realm of 30-35,000 feet maybe 40,000 or more depending on the size of the objects, i could not determine the size of the object due to the lack of a reference point or any surrounding objects and its sheer distance, its speed also seemed faster than that of a widebody airliner at cruising altitude (slightly). the object produced no sound however it could have been drown out by the sound of the low-flying airliner (which i could see/hear had departed to the east and i believe was most likely an airliner in the md-80 series or potentially an airbus a320 with the rolls-royce turbofans) i continued to watch the object as it continued farther from my field of view still shiny and reflective and fast, i could not photograph the craft accurately because i did not have an advanced lens camera at my disposal, only an iphone 5 which takes notoriously blurry and indistinguishable photos of far away objects. i considered running back into the house to look for my binoculars but at the rate the craft was moving out of sight it was apparent that it would most likely be out of sight by the time i came back outside with the binos. the ordeal lasted no more than 2 and a half minutes as the shiny, wingless, featureless oval continued out of sight before being obscured by trees and the horizon. as an avid aviation enthusiast with solid eyesight who frequently watches the skies for civilian and military aircraft and is skilled with identifying aircraft i can say that this did not resemble a conventional aircraft as it had no visible external features (wings, engines, horizontal stabilizers, vertical stabilizers or other aircraft parts that are clearly visible on large commercial airliners and military aircraft at cruising altitude) and also the craft did not produce a contrail at all although its reflection from the sun was similar to that on aircraft at similar altitudes. i don't know if the craft could have been a satellite as its trajectory was similar to one however as far as i know satellites in orbit or space stations are not visible during daylight hours (let alone in the bright sunlit late morning sky) it appeared to be too large and high-altitude to be a normal drone of some sort and the crafts identity and origin is still puzzling to me. in the years of watching the skies i have very rarely seen something i cannot identify or explain although there have been a few occasions in and around the area of plympton, ma and surrounding towns i have noticed very high, small, silver or shiny objects during bright cloudless days on at least 3-4 occasions before this, they usually appear to be at an incredible altitude with an indefinable shape due to the distance and are either entirely stationary or moving at a relatively slow pace in its position, this object was similar to those instances in its reflective nature but appeared to be moving at a more rapid and constant pace with more of a definable shape and if i were to guess it appeared to be somewhat lower. i will continue scanning the local skies, now with good binoculars at hand and will continue to report further sightings if they are to occur and try to get photo/video the next time around.