The Dow transportation average was the first of the five major equity averages to fall into bear market territory following the "leave" vote from the "Brexit" referendum on June 23.

As measured by the iShares Transportation Average ETF (IYT) - Get Report , the transportation sector was already sliding since setting its 2016 high on April 20. The largest component of the exchange-traded fund, FedEx  (FDX) - Get Report , peaked the day before, and began to slump after an earnings warning on June 22. United Parcel Service (UPS) - Get Report , the second-largest component of the ETF, will not report earnings until July 29, but it is the best performer among the three investment choices.

The two package delivery giants will be affected as the U.K. exits from the European Union. The flow of imports and exports will be in a state of flux as the U.K. and the E.U. negotiate their divorce.

Domestically, UPS has the better delivery footprint. It has a relationship with the U.S. Postal Service. When consumers enter a UPS store they can drop off mail and choose delivery options among the two delivery services.

FedEx has a disadvantage in locations near Amazon (AMZN) - Get Report fulfillment centers, as smaller packages are delivered to homes and businesses via the postal service rather than FedEx. This includes deliveries on Sundays and holidays.

So how should you trade? Read these charts.

Here's the daily chart for the Transports ETF.

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Courtesy of MetaStock Xenith

The transportation ETF closed Monday at $127.15, down 5.6% year to date. It is in bear market territory, 24.2% below its all-time high of $167.80, set on Nov. 28, 2014. The ETF is 10.7% above its 2016 low of $114.91, set on Jan. 20.

The horizontal lines are the Fibonacci Retracements of the 31.5% decline from the all-time high to the 2016 low. Note that the 2016 high of $146.07, set on April 20, was shy of the 61.8% retracement of $147.60. The first wave down held the 38.2% retracement of $125.11 on May 13. The rebound failed at the 50% retracement of $141.36 on June 9.

Following the "Brexit" vote, the ETF gapped below its 28.2% retracement, and Monday's low was below the 23.6% retracement, but odds favor a trading bounce off this key level.

Here's the weekly chart for the Transports ETF.

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Courtesy of MetaStock Xenith

The weekly chart for the Transports ETF has been negative since the week of June 17, providing a warning. The ETF is below its key weekly moving average of $135.08 and below its 200-week simple moving average of $132.65. The weekly momentum reading is projected to decline to 29.31 this week, down from 38.77 on June 24.

The weekly chart shows a red line through the price bars, marking the key weekly moving average (a five-week modified moving average). The green line is the 200-week simple moving average, the "reversion to the mean." The study in red along the bottom of the chart is weekly momentum (a 12x3x3 weekly slow stochastic), which scales between 00.00 and 100.00, where readings above 80.00 indicate overbought and readings below 20.00 indicate oversold. A negative weekly chart shows the stock below its key weekly moving average, with weekly momentum declining below 80.00 in a trend toward 20.00.

Investors looking to buy the ETF should consider doing so on weakness to $123.82, which is a key level on technical charts until the end of 2016.

Investors looking to reduce holdings should consider selling strength to $136.24, which is another key level on technical charts until the end of 2015.

Here's the daily chart for FedEx.

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Courtesy of MetaStock Xenith

FedEx closed Monday at $146.13, down just 1.9% year to date. It is in bear market territory, 21.1% below the all-time high of $185.19, set on June 11, 2015. FedEx is 22.1% above its 2016 low of $119.71, set on Jan. 21.

The horizontal lines are the Fibonacci Retracements of the 35.4% decline from the all-time high to the Jan. 20 low.

The stock set its 2016 high of $169.30 on April 19. It had been mostly above its 61.8% retracement of $160.18 between March 17 and June 22, when the stock began to slump. The stock closed Friday below its 50% retracement of $152.45, but stayed above its 38.2% retracement of $114.72 on Monday.

Here's the weekly chart for FedEx.

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Courtesy of MetaStock Xenith

The weekly chart for FedEx is negative, with the stock below its key weekly moving average of $156.63. It is above its 200-week simple moving average of $138.44. The weekly momentum reading is projected to decline to 41.96 this week, down from 54.09 on June 24.

Investors looking to buy FedEx should consider doing so on weakness to $140, which is a key level on technical charts until the end of 2016.

Investors looking to reduce holdings should consider selling strength to $153.33, which is a key level on technical charts until the end of this week.

Here's the daily chart for UPS.

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Courtesy of MetaStock Xenith

UPS closed Monday at $103.77, up 7.8% year to date. It is 9.3% below its all-time high of $114.40, set on Jan. 22, 2015. The stock is 18.9% above its 2016 low of $87.30, set on Jan. 20.

The horizontal lines are the Fibonacci Retracements of the 23.7% decline from the Jan. 22, 2015, high to the Jan 20 low. The first wave up to as high as $107.21 on April 20 was above the 61.8% retracement of $104.05. UPS was above this key level between March 17 and May 3. A decline the 50% retracement of $100.85 held this level between May 6 and May 19. The rebound that followed as to a new 2016 high of $107.58 on June 23.

The decline on Friday and Monday has the stock below its 61.8% retracement.

Here's the weekly chart for UPS.

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Courtesy of MetaStock Xenith

The weekly chart is neutral, with the stock on the cusp of its key weekly moving average of $103.68. It is above its 200-week simple moving average of $95.19. The weekly momentum reading is projected to be steady at 58.50 vs. 58.30 on June 24.

Investors looking to buy UPS should consider buying weakness to $101.32 and $93.89, which are key levels on technical charts until the end of this week and the end of 2016, respectively.

Investors looking to reduce holdings should consider selling strength to $105.25 and $108.41, which are key levels on technical charts until the end of this week.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.